98 GTP stalls when hot

This is my first post and I'd like to first of all say this is one nice forum! I found it by searching Google with my "problem". I did a bit of searching here first, as I hate a post that already been discussed and I know others do also, but I don't see the exact problem mentioned. The problem is with a 98 GTP. It has a bit over 57000 miles. A little over a year ago, we started having stalling problems after the car had been driven for a bit on warm days. All research screamed at changing the crankshaft position sensor, so last Autumn after a trip to Autozone and a small battle to break the harmonic balancer bolt free, the CPS was replaced and the car has ran perfectly.

That is up until this past weekend. Taking a 100 mile trip with the temperature in mid 80s, the car stalled again. Multiple times also. Typical scenario is cruise set at 65 (plus a bit), open highway, no steep hills, been driving for at least 30 minutes, all is fine and suddenly a hesitation is felt. I slow to pull onto the median. Tachometer is around 1500 rpm, but bouncing up and down by maybe 300 rpm or so. I'm pretty sure I noticed the TCS off light illuminate also. As I pull ontonm the median, engine is running, although barely, sputtering and non-responsive to the accelerator. After a few seconds it finally dies.

I open the hood and first thought is maybe the TCS I replaced is also bad. I happen to have some water with me in a jug and slowly poor some in the viscinity of the CPS hoping I can speed its cooling and get going, assuming this is the problem. I attempt to restart and it still has the problem. I proceed to poor water over other sensors (MAF, MAP, TPS) and wait 5 minutes or so. Atempt to restart and its running like a new car once again. The problem repeated about 5 more times until I arrived at my destination. Following day returning home, the temp was a bit cooler (low 80s) and the stall only occured 1 time.

No service engine soon light. I have a scan tool and no DTCs are set. I'm speculating it may be the Ignition Control Module, but hate to just start replacing parts and guess whther its really fixed or not. I thought surely the CPS was the problem based upon other descriptions, but either the replacement I installed is also bad, or it wasn't the problem in the beginning. Anyone have any ideas, suggestions, similar problems? Thanks in advance for any input.

Dan

Welcome to AF.

Normally when a crank position sensor goes out the stall is abrupt and the engine dies immediately. As a minimum I would get the ICM tested at Autozone. Have you checked fuel pressure to see if it is in specs?

Welcome to AF.

Normally when a crank position sensor goes out the stall is abrupt and the engine dies immediately. As a minimum I would get the ICM tested at Autozone. Have you checked fuel pressure to see if it is in specs?

Thanks for the wecome and the reply. Just knowing that the CPS failure causes an abrupt stall is something that I haven't heard directly stated on any site, yet it definitely makes sense when you read between the line. Just knowing this is an incredible step as at least I won't be wasting time in a useless area of diagnosis. Unfortunately I don't have a fuel pressure gauge (at least not for the GP), but I agree that testing makes sense and it wouldn't hurt to get one. Hopefully tomorrow I'll see if the local Autozone can check out the ICM. Once again, there are no DTCs and this is a big reason why its so difficult to nail down the problem. I've sorta ruled out the fuel pump and screen since there is no direct way engine heat is effecting these, yet I realize that issues like relays, wiring and the fuel pump resistor may be suspect. Once again thanks very much!

Dan

Well, not exactly a great day for problem solving. After checking with Autozone, Advance, Carquest and Pep boys, all told me they did not have proper test equipment for testing the ICM for my 98 GP. Finally though, the local NAPA store came through and had the goods for testing the suspect module. Bad news though, after running the test twice, it passed both times. I explained to the gentleman that the failure only occured on hot days and after an extended driving period (i.e. hint, maybe its not hot enough on the tester to fail like I'm seeing). In any case, he assured me the module was OK.

Now I'm back to the drawing board. I still suspect the ICM may be the problem, but hate to dish out $200 on a hunch and I'm hesitant at buying one of the $60 ones, even though these may work fine. Anybody have any reccomendations on replacement ICMs such as Wells, Sorensen or other non-OEM brands? I'm trying to think what may cause a low fuel pressure condition (maybe wiring or a relay????) that happens only when the engine compartment is hot as I certainly can't rule this out either, but still not seeing any ovious leads in this path either.

Dan

The temperature is finally getting around 90 now in this part of Florida, and I've picked up a fuel pressure gauge, so I decided it was time to try to get a little farther along with this problem. I decided to drive the car into work (only 5 miles) and sure enough it stalled twice just as I was about to park the car when arriving back to work after lunch. Made the drive home at the end of the day, and got set to try to repeat the problem. Sure enough, after about 5 minutes of idleing in the driveway, it started happening.

I connected the fuel gauge and what I observed was that indeed the pressure was dropping down to about 10 psi when the problem would occur. FYI, the pressure after the prime is about 50 psi and steady state after its running (not dying yet) was about 42 psi. I've read plenty about the fuel pump relay, so I wanted to investigate this a little farther. Now here's where I'm getting a bit confused.

I actually removed relay 15, which is labeled as the pump speed relay. I expected the pump not to run at all. To my amazement, the pump would prime, and the car would crank and the pump seemed to be running, even with the speed control relay removed! :screwy: I looked in the manual and there are 2 slightly conflicting diagrams. One appears to show that the ouput of the fuel pump relay goes into the pump speed relay, and based upon whether the pump speed relay is energized, either a direct +12 or a path through the resistor is taken. I obviously can't believe this as it would be impossible for the pump to be receiving power. By the way, with relay 15 removed, I would still get a repeated failure after about 5 minutes or so. Another diagram seems to show a path out of the pump relay through the resistor even when relay 15 isn't installed. Can anyone verify this?

So, something is causing an interruption to power to the fuel pump only when its hot outside and only after the engine compartment has been well saturated with heat. I haven't read a case where the FPR has failed in this manner, but I haven't ruled this out yet either. Next oportunity, I need to verify whether its the FPR or not. Still of concern is a statment in the manual - "The fuel pump relay will remain ON as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped."

From this statement, it sounds like if the CPS signal into the PCM is disrupted, the PCM will turn off the pump. I need to verify whether or not this is occurring as well. I've been suspecting the ICM all along and I assume its in the path of the CPS pulse getting to the PCM. Again, I replaced the CPS a little while back, so I'm not suspecting it as the culprit. Also, the engine doesn't completely die, it just stumbles and misses really bad and eventually dies after maybe 10 seconds. Ignition is happening, but looks like no fuel.

Dan

Try this trick from our tips and maintenance sub-forum (thank our awesome moderators GTP Dad and bnaylor). If the car no longer stalls with the fuel pump resistor bypassed, then it's your problem. The resistor will definitely fail due to heat. If nothing changes, you may need a fuel pump assembly.

http://www.automotiveforums.com/vbulletin/showthread.php?t=658282

Well, as my luck would have it, I drove the car today, and no failure. I was all set with a meter ready to see if when it failed I was losing the signal to the fuel pump relay or not and if this checked out OK, I was ready to try the bent pin on the pump speed relay if I could get it failing repeated like yesterday. It must have been a few degrees cooler, different humidity or something, but it ran perfect. I decided to inspect the fuel pump resistor anyway, so I dug in and removed it. It looks fine, yet its still a prime candidate for being the troublemaker. I'm thinking about using a heat gun to add a little extra to it and see if I can induce the problem. I removed the passenger side headlight to get better access and found the lense had come unglued to the housing. I used a little marine adhesive and clamped it. Hopefully this will hold it together once again.

Dan

Ignition control module will not fix it. I just replaced mine ICM and it fixed some of my other issues, (fan speed switch on my climate control, and headlights cutting out when climate control is turned on). It how ever didnt fix my hesitation problems. Mine is doing the same thing.

My ICM went to an all new low just before I replaced it. It wanted to start the car while the ignition was off. :screwy:


Im going to try the resistor by-pass as suggested to see if it helps me out. Sounds like a good possiblity anyway. This is all getting too costly and old for me. :banghead:


GotoGod

Its been a little while since I've posted about our 98 GTP problem, so here's a short recap. Problem is an intermittent stumbling, stuttering and finally stalling. Seems to happen on warm/hot days or after driving long enough to heat up the engine compartment. No DTCs are being set. Key point and major complicating factor is its intermittent. Initial suspicions pointed to the CPS, so changed it last year. Ran fine until warmer weather in late Springtime when problem started happening again. Tested the ICM and it passed the tests at local automotive store.

A few months ago, finally got a fuel pressure gauge, was able to get the problem to occur with gauge connected and observed a fuel pressure drop down to ~ 10 lbs when the problem would occur. Began suspecting the fuel pump resistor and about a month ago replaced it with the FPR relocation kit. car ran fine..... until today:disappoin .

Friday the 13th. I should have known. Yep, its still doing it. Car sat in sun all morning, drove about 6 miles, temp ~95 degrees, and boom, same problem. I observed the TCS off light came on. After pulling off on the side of the road, I also observed the fuel pump would run to prime when switching the ignition off and on, but it would restart and still wanting to stumble. After about a minute of letting it sit, it did finally restart and I got to where I needed to be.

So here's what I'm now thinking and I humbly ask for anyone's input to let me know where I'm off-base.
1. I think the low fuel pressure I witnessed previously may have been a side-effect of the actual problem. My understanding is if the PCM doesn't receive indication from the ICM of engine rotation, the PCM does not energize the fuel pump. I think this is what actually is happening and not a problem with the FPR or fuel pump in any way.
2. I don't think I have a CPS problem since its been replaced less than a year ago, and mostly because from other's psost, when the CPS is bad, the engine dies abruptly and totally. This is not the case for our car since it continues to stumble and try to run for several seconds or up to 1/2 minute.

Even though the ICM tested OK previously, I think it is really intermittently having a failure when it gets hot. Its either causing misfiring and/or simply not sending the indication to the PCM of crank rotation which will cause the fuel pump to be turned off. Anyone think I'm missing something or does a new ICM sound like the next step? This would be so much easier if it wasn't so intermittent, but at least so far it hasn't occurred in a situation to cause an accident.

Thanks for all the help!
Dan

when the trac off light came on, did you notice the tachometer drop to zero at the same time? If so, that is a classic symptom of a bad crank position sensor. A bad CKPS will also cause hard starting/long crank time, random stalling, and fuel pump shut off. It can also fail when it gets hot, and then work fine once it cools off.

Thanks for the reply. No, the tach does not go to zero, it bounces around erratically from 0 to around 800 RPM. Once again, I changes the CPS last Autumn. Also, once again, the car does not completely stall, it stumbles and runs rough for several seconds up to 1/2 minute when this problem happens. The fact that it doesn't completely die leads me to the conclusion that it is not the CPS.

Thanks once again,
Dan

If I had a dime for every time someone stated "I recently replaced the ______. so that can't be it!", I'd be typing this from my own Island in the Carribbean. Your problem still sounds like a CKPS to me. One thing to try, unplug the MAF (Mass Airflow Sensor). and see if the car runs better. A MAF will exhibit strange stalling/performance issues without tripping a code.

richtazz, I appreciate your input. Please tell me if I'm wrong about these facts. First of all, reasons I find it difficult to believe its the crankshaft positioning sensor:
1. The problem occurs in the exact same manner, both with the replacement CPS and with the original.
2. The problem is not a complete shutoff of the ignition system. The car continues to sputter and stumble. After reading other posts describing CPS failures, indications are with a CPS failure that there is a complete and instantaneous shutdown of the ignition system. This is not what I'm experiencing.

I also find it difficult to believe its the MAF. Would the MAF cause the PCM to turn off the fuel pump? If so, then I'll put that on my list of suspicions, but I've not read that fact anywhere. The only thing I've determined for 100% is that if the PCM fails to recieve an indication from the ICM that the crank is turning, then the PCM will turn off the fuel pump. I realize that the ICM must receive its signal from the CPS, but due to the facts stated previously, I'm hesitant to replace the CPS again and expect to solve the problem.

Thanks again for all of the help!

Dan

I found an ICM at a reasonable price, so I had to try it. Everyone who said this problem isn't the ICM.... you're right. I finally had a few minutes to troubleshoot while the falure was occurring (even though as my luck would have it I wasn't at home :banghead: ). So here's the latest of new info :

1. I unplugged the MAF as Richtazz suggested and finally actually got a DTC :) , but the problem unfortunately remained. At least the PCM is smart enough to know the MAF was unplugged.
2. I was getting the problem to occur while sitting parked, and I did not see a Trac Off indicator this time.
3. I was able to observe what I hope is key to getting to the bottom of this problem. There was a distinctive change in the sound from the fuel pump as the problem would occur. I had the AC off (man it was hot!:lol: ) and opened the access door to the trunk so I could hear the fuel pump running. I wanted to detect if the fuel pump was instantly turning off when the problem occurred since I've suspected this to be the case. What I discovered sounded like the voltage to the fuel pump was gradually changing (over about 10 seconds) as the pitch would noticably change and then the car would start stumbling and stuttering and finally die in its usual manner. If I tried to instantly restart, I'd hear it prime, but I couldn't tell for sure if the pump was running normally or not. So it looks like there is NOT an instantaneous stopping of the fuel pump caused by a loss of crank signal as I have suspecting all along.

First thought goes back to the fuel pump resistor. I know about the test for the fuel pump resistor bending the pin on the fuel pump relay, but again, I wasn't home and didn't have any tools with me to do this properly. I just recently installed a new fuel pump resistor with the relocation deal, so I'm not sure this is the problem, but almost certainly somewhere I'm losing voltage to the fuel pump. It may actually be the pump, but it only appears to occur when the weather is hot, so I don't think its the pump itself failing.

Any suggestions where to check for a possible bad ground point or voltage supply to the fuel pump that may be heat related? My next step (if I can get the problem to occur while I'm at home) is to measure the voltage at the pump and at the relays and see if I can trace to a point where its not as required.

Thanks again for all of the wonderful help!
Dan

Got home and was able to get the problem to repeat at home. I removed the access cover to the fuel pump and listened once again as the problem repeated. Now that I could hear even better, I realized the change in pitch didn't sound like the voltage dropping after all, but more like the pump was running dry! I decided instead of putting the meter on it that the first thing to do was pull it and see what it looked like inside.

This was the first time I've looked at the pump. Definitely made easy to remove, not a bad design at all. After pulling the pump, the outer filter screen looked pretty good, so I seperated the assembly to see inside. A second filter screen inside the pump wasn't so clean. There was noticable debris inside the enclosure and the internal screen was coated with silty material. Definietly needed cleaning, but could this be my only problem all along; a dirty screen that's preventing fuel from entering the pump? Has it just been some wild coincidence that the problem appears to only be happening in hot weather??? I'm planning to drive it some more tomorrow to see if I made a difference.

After reinstalling the pump, I can't hear any noticable noise at all from it now. Fuel pressure looks good being just shy of 50 lbs while running. This certainly will help, but its still just too wierd that the problem appears to be somehow heat related. Maybe something in combination with the evaporative control system? Anybody have any clue how temperature could effect a fuel pump in this way?

Thanks once again for all the help,
Dan

So far, so good. I haven't driven enough to know for sure, but no problems today after cleaning the inner fuel strainer. I read a bit about the fuel pump and its canister to avoid starvation due to fuel sloshing around. I still can't explain what effect if any heat would have on the fuel pump acting this way due to having a partially clogged strainer. I also can't understand how the outer strainer was fairly clean, but the inner strainer (the one actually on the pump) wasn't. After I drive for a few more days, I'll post if this indeed looks like the final solution (if anyone here cares).

Dan

OK, its been a month now. I've driven the car multiple short trips and a few long ones and no problems. I'd say the fuel strainer cleaning has solved the problem. Again, still can't explain the appearant relation to being heat related, but nonetheless its fixed and reliable once again. So advice to anyone who has random stalls, take an hour and check the strainers on the fuel pump before spending a dime on replacement electronic parts. This could be all that's wrong.

Dan

Wow! You da man! I have a '98 GTP since '98 and about once or twice a year at completely random times it starts running real rough and starts stinking real bad. It seems like it's going to stall but never does. All of the suddden, it clears up and runs great. I wonder what it might be. Unfortunately, I must wait until it gets worse to fix it.