'97 Grand dies when I stop giving it gas

[rick465]

I just replaced the PCM (and went through hell trying to get the correct one) now it cranks and runs just fine...BUT whenever I let off the gas the RPM's just go all the way down and it dies. I have idled it for nearly 30 minutes at between 1000 and 1500 RPM's and it still did the same thing. No check engine light is on so there are no codes. 1 odd thing too. About 8 months ago I had a mechanic replace the freeze plugs because they were leaking. Now I am getting steam out of the same place again. It was dark and I couldnt tell exactly where it was coming from but that shouldn't cause the dying issue.
What the heck?
Any ideas. Thanks guys!

 

[JPNinPA]

Overheating can kill the engine.

Start with cleaning the battery terminals and ground connections.
Then clean the TB and IAC
Check your fuel pressure with key on and engine off. And at low idle 1000 will work.

Track down the leak it may be possible you have a bad head gasket or a cracked head.
To check for a cracked head check the oil in the water or the water in the oil.

To check for a bad head gasket check if the exhaust is white and steamy or smells sweet. There is also a test for exhaust gas in the coolant.

Regards,
JPNinPA

Sent using TapTalk

 

[k-2]

I will try to help
some info needed
Wich engine?
Why did you change PCM?

It is incorrect to assume no CEL no codes. Also the key trick will NOT so all codes...

Holdig Throttle open often suggests over fueliing OR a TPS issue.

Did engine overheat OR freeze plug changed due to leaking

suggest you scan post codes, answer questions - maybe do fuel pressure leakdown and Vac leak ck

 

[JPNinPA]

It is incorrect to assume no CEL no codes. Also the key trick will NOT so all codes...

Holdig Throttle open often suggests over fueliing OR a TPS issue.

Did engine overheat OR freeze plug changed due to leaking

suggest you scan post codes, answer questions - maybe do fuel pressure leakdown and Vac leak ck

Agree
And holding the throttle open also means the IAC isn't working to keep the engine running.




JPNinPA
Using Jeepz.com app

 

[rick465]

4.0 straight 6. Freeze plugs replaced because of leaking. Terminals clean. No smoke. Water coming out is clear of oil. (will have to check tomorrow if any water comes out when the engine is off) Engine temp remains fine. No check engine light is on. Not a security issue. That was fixed with the PCM replacement. That replacement was done because the Jeep was stalling and running rough. It seemed to preform better when I 'messed' with the PCM, then only when I was pushing or jiggling with it. Now it starts right up and runs smoothly until I let off the gas.
I don't know what an IAC or TB is and I don't know how to check the fuel pressure. I'll see what I can tell on the vacuum leak part.

 

[JPNinPA]

IAC is the idle air control on the TB. It is what sets the air level for the engine to idle at 750rpm
TB is the throttle body that the IAC and TPS are connected. It is cable connected to the gas pedal. When you step on the gas it opens the valve in the TB letting more air in. The TPS is the throttle position sensor that reads how open the TB valve is and sends the signal to the PCM to regulate the injector firing time and duration.

http://www.jeepforum.com/forum/f9/c...te-up-dummies-1114849/#/topics/1114849?page=1


JPNinPA
Using Jeepz.com app

 

[k-2]

Quick - question does the CEL come on at start up?

 

[rick465]

Great thread JPNinPA!!! Thanks! I'll do that for sure. Yes k-2 the CEL comes on when I turn on the key and crank it.

When I got back to it today I tried to start it and the battery was dead, just the click you get when you leave the lights on all night. (just a note, it started hard like the battery was low yesterday) I hooked up the charger and within 15 minutes it showed fully charged. (So does the multimeter). I turned the key and got the normal signs from the gauges for startup. I cranked it and got nothing. Then there was a fast clicking from behind the glove box. I had seen this might be a security thing. I have no alarm system on this Jeep. But I turned the locks (doors and hatch) with the key 3 times and then got in and tried to lock and unlock the doors with the button. No power. I hooked the charger back up and it showed it was charging (no longer fully charged). The electric lock then worked, so I did it back and forth 3 times. I tried cranking again and got nothing but the click behind the glove box came back.
Im staying away from my .44 for the moment but threatening the Jeep hasn't worked.
Oh yeah, since I couldn't start it, I couldn't move it. It's facing a downhill grade and I was going to face it up hill, put water in the radiator and see if it comes from where the freeze plugs are. So there's still that.

 

[JPNinPA]

You battery is likely shot but I want to mention about cleaning and checking with a multi meter. Engine off should read 12.6 V anything less is an issue. Running should be 14.4V. That only tells you it's not dead and it is being charged. Load testing a battery is crucial. It tells you the CCA cold cranking amps. That is the reserve power to turn the engine.
Also with low voltage or poor connections the engine could run rough to stall. Yes even when you read 12.6 and 14.4V...


I had an issue where the jeep would just shut off. It was a loose battery connection.


Also the above tab cleaning should be done every 30k miles or so.

Regards,
JPNinPA

Sent using TapTalk

 

[rick465]

Every 30k?!? I guess I'm a bit behind on that one at 180k. HA!
I am going to have the battery checked again, you are correct on the testing I have been able to do. I'll run through the connections too as I can.
Awesome help! THANKS!

 

[rick465]

UGH! Had the battery professionally tested and it WAS bad. I got a new one and put it in. Bam! Started right up but, of course, died immediately when I let off the gas. I tried to start it again and had no power. No ignition, dash lights, dome lights or anything. There was also a weird 'beeping' coming from behind the driver side dash that sounded like it was on the left side of the steering wheel. It stopped when I turned the key back on and off. I took off the positive battery cable and put it back on. I had power. I turned the key and the dash lit up then cranked it... nothing and then no power. WTH! I could not find any obvious bad connections or shorts. Ridiculous! What could this be? A bad connection or short I am missing? Doesn't seem to be a CPS issue, yet anyway. Any ideas for the pitifully uneducated would be great!

 

[rick465]

Sorry about filling this thing up but I only have limited times to work on this fool thing. I got it running by (I think) wiggling the negative cable. So, I'm guessing the issue is there. I went to get the Jeep on an up hill surface to see if the water was coming from the freeze plugs it seems. I am going to have a 'conversation' with the guys that replaced them last year. BUT the Jeep did not die when I let off the gas?!? Maybe the PCM needed more time to learn or maybe the battery was screwing with it. No idea. I am sure things won't be the same next time. I'll let you know. But if there is anything else that comes to mind, I'd love to know.
Thanks again guys!

 

[JPNinPA]

Refer to my first reply. Look at both ends of the power and ground leads. The contact points should be clean with no corrosion. If your not sure disconnect and lightly sand to a shiny metal appearance. Do thin on Both sides of the connection and reconnect. There should be a ground to the engine and one to the body. You might also inspect the wire itself. Many times the wire corrodes in the wire coating. If you suspect wire corrosion look into the big three upgrade.



Bad connection can create a number of weird issues that you could end up spending list of $$$ on. And put this on your once every year or two maintenance checks.



Regards,
JPNinPA

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