85.5conquest

Thanks for all the info you've been a great help. I have a smaller Sears store near me and I'll see if I can get my hands on one of those gauges. I've known I need one for a while now, just haven't spent the time to track one down. Worst case I have someone that can help me out so we can try blowing into the hose. Do you know what the O2 sensor should be reading at idle for a warmed up engine? I know the .7+ I've been getting is too high, but should I be looking for something in the .2 range? .5?

Thanks for the info I'm very happy to hear it can be this simple of a fix. I'm assuming your talking about where the ECU & O2 sensor diagnostic connector is. I looked in there and saw only the ECU & O2 connector (3 pin) and the fuel pump testing terminal (1 pin) as terminals that ended in that location. I checked the supplemental manual wiring diagram and it only shows these two connectors unless I'm missing something. Does this mean I should be connecting two pins of the ECU & O2 diagnostic connector? If so could you tell me which wires, as I really don't like shorting wires together unless I know exactly what I should be doing. Sorry to bother you with the minor details. I checked my service manuals again and didn't see a procedure for shorting any pins it in either book. Am I missing it? All I see is in the beginning of the electrical section of the supplemental manual it states that a altitude correcting feature was added?

Vin F which the book I have makes it a 85. It has 5 lug wheels and a intercooler & intercooler tags. So either the guy I bought it from went through a lot of work to change it out or its a 85.5? Also I have not replaced the injector plugs, but ordered them today so I'll get that done. Does anyone know of a way to make a nice connection with the replacements? I don't know how picky the PWM for the injectors is going to be. All I've done before is use crimp connectors, solder the lines to the connector, and heat shrink it. Will this be good enough? Engine 10 btdc before I took it to smog with warmed engine and vac line removed. Just checked timing movement w/ and w/o vac advance and it increased smoothly. Advanced more with vac line attached and when attached @ high RPM jumped a lot. I live @4000 ft but I'm getting it tested at like 200 ft so I'm setting it @ 10 btdc for now. Ill have to change it for the altitude when I'm done though thank you. Used a hose to pull a vacuum on the distributor diaphragm. It held a vacuum but squeaked a little as it was applied. Assuming this is just the metal against metal movement inside? Fuel pressure vac line had no fuel in it, and regulator -should- be good as it is new. When the old one went out the car barely ran, so it cant be as bad as the OE one... I tried to take the hex plug out and your right that thing is in there tight... I'll have to buy a 6mm allen socket to get it off after using some penetrating oil on it. I just have wrenches and they're not gonna do the job. As for O2... I was watching it as I warmed it up today, and it seemed to increase in voltage as the car warmed up. It started around .2 and when the car warmed up it was reading .7 at idle. This made me think the coolant temp sensor (which is about 1 month old) is bad, but it was 310 Ohms warmed up (read it when fan started to kick in) and 2.2K when cold. Book I have seems to agree with these values and I believe you said 300 when warmed, so I guess its fine? The O2 sensor -did not- jump between voltages, but I just have it at idle. It stayed constant and basically increased in voltage by the thousandths digit. O2 sensor is new, and I was reading the voltage @ the diagnostic port on the passengers side. If there was a short in the wire it would pull the entire wire down to 0V, not just @ the ECU right? So I doubt it's a short in the wiring. Also O2 sensor changes if you rev up the engine, increased w/ rpms and drops when you suddenly close the throttle. When I was setting the idle point I tested the idle nose switch. It was opening and closing the circuit with it being depressed. I also didnt have to rev it up to 3K to see a drop in the O2 sensor output, so unless I understood you wrong it looks like the nose switch is doing ok. That leaves vacuum leaks. I'll have to go through and replace all the lines to make sure they're ok. That and check the fuel pressure. Thanks for the input everyone. I'll get back to you when this is done.

Sounds like you may have a exhaust leak, most likely in the engine compartment. When engine RPMs are higher your pushing more air out of the engine, through the exhaust pipe. This raises the pressure and any leaks in the system become worse. If this is the case its most likely in the engine compartment as it can come through the firewall into the interior from the engine bay. Other leaks will tend to get blown away and not enter the interior if I remember right. Look for black carbon buildup around the joints of the system, and the components near them. Also if you have someone that can help you, block the tires, start the car and have them hold down the brake. Then have them press on the gas lightly to put a load on the engine. You can then place your hand near the joints and feel for exhaust being pushed out of the joints. BE CAREFUL if you do this and make sure your out of the way of the car in case it moves. If you feel any warm air being pushed out you need to fix that leak.

I can confirm that both injectors have black tops as well as J stamps. Also once they were cleaned they did flow at the same rate, I was present for the test. We also tried swapping the injector sides to see if the primary was tired, but the car ran the same so I swapped them back. It's more likely that the ECU I got isn't a 87 as I have heard that they will be noticeably wrong upon start up from a guy I was speaking with on this site, and mine seems to run better when driving and the same at idle. When I bought the ECU I was told to match a stamping mark on the body, which is how I went about shopping for the ECU. I don't remember the stamp but if its important I can go get it. Also since I bought the car from the original owner I'm almost certain its a 85.5. He even had the 85 shop manual & .5 update book from the dealer (mitsu copy though, which I don't think makes a difference since they made the car?). As far as blockages in the exhaust I pulled off the check valve in the secondary air injection system that connects into the back of the turbo and watched for a RPM difference at idle. There was no difference after introducing the exhaust leak. The only other way I can think of to look for blockages is to actually remove the exhaust system which isn't too bad but kinda a pain. Is there a better way? Even if the stock ECU is installed the car runs 10X above the limit for CO, so either both ECU's are bad and ones not a 87 as it was advertised, or the problem lies somewhere else. Has anyone sent their ECU out to a company such as A1 Cardone to get it repaired? When looking for the ECU the local shops said that there weren't a lot of ECU's floating around so they couldn't order them, they had to send mine in to get it reworked. Although I'd like to go this route with the ECU, as this is one of the few ways I'll get a warranty on it, I don't like the idea of letting the stock ECU go. I was wondering if anyone had tried to get one re-worked and what the results were? Any other thoughts as to what could be causing this or things to test? Thanks for the replies everyone. Also I passed smog 2 years ago with this car, and it passed it right before I bought the car. So if the injectors were incorrect for the car I believe that it would have been caught at one of these checks rather than now, but I could be wrong.

Ya set timing to 10 btdc. Thanks for the reply.

I have an 85.5 plymoth conquest I have been trying to smog. It is running at 10% CO, and I am told that it should be running below 1% from the tech. I was wondering if anyone had some advice as to what could be causing this. What I’ve done… Replaced: Fuel Pressure Regulator O2 Sensor Plugs/Wires/Cap/Rotor/Fuel & Air Filter Cleaned Injectors TPS tested fine ISC seems fine Tried a ECU off a 87 and still runs @ 10% O2 sensor is reading about 1V, which I am told is rich. It is also drops in voltage when the RPMs drop after reving the engine, which tells me its working. I have not tested the fuel pressure as I do not want to cut into the feed line, and I see no port to test the pressure. Spark plugs are brown, so it’s not running very rich. Also HC not being high tells me same. I was advised the ECU was the problem as it is receiving a rich signal but not leaning out the mix. I was surprised that 2 ECU’s would have the same problem. With the 87 ECU the car also has power surges off and on when you approach the barrier between vacuum and boost slowly (~0 PSI). If you floor it however it passes the barrier fine, but does not seem to have the power it should. The stock ECU runs worse. The car doesn’t have the power it should and misses/surges more, and around a larger band on the boost gauge. I didn’t know if the car has a control valve on the turbo to control boost pressure that could be sticking or not working properly? Or if the MAP sensor could be off causing it to run rich? Sorry for the long post, and thanks in advance for any tips you can send my way.

Ok so I feel pretty stupid. I found out that a ghetto repair by the previous owner to the heater control valve (manual cable) was getting in the way of the throttle pedal movement. Once I removed the cable there was no binding on the throttle movement. Put the ISC back on the car and ran it, and it's idling correctly. However when I give it gas, it increases in RPMs fine but when the RPMs decreased the ISC stops the throttle lever at about 2K RPMs, and then lowers it in steps of about 500 RPMs until it reaches its correct idle speed again. The decrease is slow and takes much longer than it should. This along with the ISC taking longer to retract than to extend when off the car makes me think that its time to replace it. Called the local wrecking yard and they don't have it, same with the local auto parts stores and the Dodge and Mitsu dealers, and I also checked RockAuto as suggested by Killtodie previously and they either cannot get it or have the wrong part listed. I was wondering if anyone knew a reliable place to get one of these, or was parting out a car that might sell me one. I have found the motor online, but I would prefer to get the entire assembly if possible. Mine has one round connector with four pins inside of it. Thanks again to everyone who has been helping me figure this thing out.

Thanks again everyone for the info. I checked the connectors on the ISC and they seemed to have nice solid connections. I did not see the clip Indiana was talking about, could this be a possible problem? Also my ISC has four leads, two going to the motor and two to the housing. The two leads to the housing are basically shorted when the button is depressed (13ohms) and they are open when I let go of the button. Is there a way to open up the motor/housing assembly and re-grease it (assuming 25yr old grease might not be the best) to see if that smooths its operation? I played with it a little but it didn't seem to want to come out any further then about 1/4", and I didn't want to break it. Wanted to see if I could smooth it out before I try putting everything back together. As for the throttle cable I will try lubricating it tomorrow, and replacing the ground cable just to be safe. The throttle return spring seemed to be pretty lively when I was taking the throttle cable off. I don't know if this is stock but mine has two springs, one inside the other which seem to have a good pull. I'll check them when I get everything back together just to be safe though. I'll take a look at the cruise control cable also. I know that the main cable going by the turbo was getting hot, as the insulation has a one foot section that has been peeling away even though it was routed around the turbo. It may just be a band-aid for now but I put some liquid electrical tape on that also to keep it from shorting something out. I never use the cruise control anyway though, so I might as well disconnect it.

You guys are awesome, thank you for the help. I took the throttle cable end off this morning and the car idled correctly. I played with the throttle cable and it seemed to move smoothly though. I then gave it a little gas and when I let off the idle stuck for a bit then returned to normal. I pulled the ISC and tested it, and it extended smoothly, but on return it took longer and seemed to struggle a little more with the same supply. Repeated this a couple times to make sure I wasn't dreaming. I'm assuming this a indication that the motor is going out and needs to be replaced? Also since I removed the ISC previously and ran the car with just the throttle cable connected (and it still ran at 3K) does this mean I may be looking at both the cable and the ISC? If so do you guys know a good place to get the ISC motor and the throttle cable? By the way the TPS reading dropped to 0.2V after I disconnected the throttle cable.

Sorry I forgot to mention that this was one of the first things I tried. I swapped back to the stock ECU this morning again and checked, no change jumps back to 3K RPMs since it's cold. Is there any special type of reset or something that has to be done when changing back to the stock ECU to clear this problem? I had the battery cable disconnected while doing the work of course. Also this problem occurred after the 87 ECU was working fine for a couple hours, not immediately after I installed it. "You have injectors that have an "H" or "J" stamped on them? The 85.5-86 is when they changed to the "J" injector although those are swapped with "H" since they are, or appear to have the same size orifice. " I looked at my injectors tonight and right below the connection port they have a square symbol then a J52R on them. I think the R is upside down vs. the other letters/numbers though, was looking at it with a mirror. Is this the "J" you were talking about? I think the injectors are stock since the car only has ~80K miles on it, and I bought it with ~60K. The guy I took the injectors to said that they had the same flow rate. Didn't get a chance to check the timing/vacuum/cable this morning due to work, but will work on that tomorrow if possible. Also is there a way to check the pressure sensor output? I have removed the vacuum line from it to test it, and the RPMs increased dramatically, but the boost sensor read about -2. I was assuming it should read 0, but I also didn't know if the altitude at my location would cause that (4000ft). Also please forgive my ignorance but is it even possible to check the timing when the engine is running at 3K rpms? I just have a standard timing light, not a expensive one where you can adjust the advance and read the degrees from that. Thank you both for your input. I really appreciate the help.

I replaced the ECU with a 87 after I was told it would be compatible. It seemed to run fine (well the same, not fine) when it was installed (had at least 2hrs drive time on it when the problem happened). Could the ECU have caused the problem? If so is there something particular I should be looking at since swapping back to my stock ECU did not fix the idle problem? I'll change it back in the morning and check over the vacuum lines and throttle cable. Thank you very much for the info.

I checked around for a vacuum leak today. All the hoses seem to be intact. I pulled a small vacuum hose off the throttle body which had no effect, and disconnected the PCV valve from its hose, which increased the RPM's noticeably. I also went around the throttle body with carb cleaner to try to see if I could hear a increase in RPMs, but couldn't hear anything. I don't know if that was because of the already fast engine speed though. Does the increase in engine speed from the PCV line mean there is no vacuum leak? The engine speed returned to normal when I capped the line with my thumb, and I could tell it was pulling a vacuum. As for the TPS - I pulled the TPS off the car and measured its resistance. It seemed to change smoothly and had no dead spots. I put the connector back on the car and started it up, and at idle the engine runs fast as normal, but if you move the TPS arm to create a signal like the pedal was being depressed the engine starts to stumble and fall on its face. If you depress the pedal (open butterfly) while the TPS is off the throttle body but connected (arm @ idle), the engine RPMs increase without hesitation and fall when you let off the pedal. Originally the TPS signal voltage at idle was ~1.5V and adjusted that down to ~0.9V which didn't seem to have an effect. ISC - I removed this from the throttle body but kept it electrically connected as discussed before. The car ran the same without it being connected to the throttle body. I have not gone and reset the ISC as I do not know how. Is there an adjustment on the TPS ISC or something else that can go bad enough to cause the idle speed to be off by 4K RPMs suddenly? Also I forgot to mention I messed with the boost sensor previously. I pulled the vacuum line off the boost sensor (which was pegged on the negative scale) and when it came off the engine speed increased, and the gauge read about -2 (could be because of the altitude? 4000ft). Placed it back on and the engine slowed down and reading went back to negative. Any thoughts or comments? It's really confusing me.

I was hoping I could get some help to get my car back on the road. I have an 85.5 Plymouth Conquest. Currently when you start the car the idle speed races up to 3K rpms, and stays there if the engine is cold. When the engine is warm the idle speed jumps to ~4.5K at startup, and stays there. Anyone have any thoughts on what could be causing this? It started when I was driving down the freeway (had been a couple of hours of driving, but not continuous). Here’s what I know / have tried. Fuel Pressure Regulator – problems started a while ago when this went out. Was replaced and mostly fixed the problem. The car ran pretty well, but seemed to have a slight hesitation around 3-4K when it was pushed. It would also not pass smog (HC too high). When trying to get it smoged this idle problem occurred. Have warranted out the new regulator, and a newer one did not fix the problem. Throttle body – butterfly valve is not stuck open. Operates freely. TPS – resistance changes smoothly when arm is moved, at idle it reads ~.9V at sensor and ECU. O2 sensor – has been changed out recently (trying to pass smog). Starts at about 0.4V and rises to 0.7V quickly (assuming this is the warm up period). ECU still provides an O2 sensor trouble code that does not clear out for some reason though even when the battery is disconnected and the car has not started when codes are pulled. ECU – Have replaced, no change in operation. Have not checked trouble codes on 2nd ECU. Again replaced when trying to get it to pass smog and quickly swapped back to make sure it wasn’t the ECU causing the problem. Injectors – Had them cleaned and tested. They are opening and closing correctly and are flowing at the correct values according to the shop. Trouble codes – have messed around with different sensors and unplugged them to see effects. Have received and cleared (disconnected battery) TPS, coolant temp, MAF, codes due to disconnecting and reconnecting terminals. This indicates to me that they are working correctly? Coolant temp sensor was replaced trying to smog it (2 terminal). Wiring Harness – had some wires with some insulation gone on the outside of the ECU harness. No wires were touching and none of the copper seemed to be effected. Repaired with liquid electrical tape, no effect. Idle Control Solenoid – can hear what I believe is this moving when I turn the key on. Removed it from the throttle body but kept connected and started the car. Had no effect. I don’t get it… anyone have any thoughts please?