Surging and Stalling
 

On my 95 I just had the fuel injector, fuel pump and gas tank(new gas in it) replaced by a reputable guy. He said everything checks ok. My truck- when running surges (idle) high/low.Even when I'm stopped at a light, then it'll stall. Now it's stalling out whenever I'm stopped. It even stalls if I'm cutting the wheel to make a turn. In a straight line it runs great, lots of power. It sets no trouble codes at all. The check engine light does work. I just tuned it up. All what was wrong were the plugs were a little fouled because it would idle for long periods of time. This truck has sat for about 2 1/2 years. It would get started every once in awhile during that period, but not very often. Funny thing is, I live in NJ and we do emissions here and passed with no problems. I've never changed the O2 sensors ,tps, iac, or any other sensor since I've owned it(about 7-8yrs). Wouldn't it throw a code if a sesor went bad? Before it was parked this thing ran like a champ with no problems at all! It has 193,000 miles on it, but the original owner replaced the motor with a brand new Jasper engine. I bought it around 144,000.
This truck almost got me killed tonight trying to cross an intersection! Would anyone have any clue on what might be wrong or what should I check/replace? I really love this truck but I'm getting so frustrated with it!
Thanks for any and all replies.

1995 has two different types of injection systems. Which engine do you have?

If the engine look like this you have CMFI:

http://i561.photobucket.com/albums/ss58/cwhook/CMFI.jpg



If it looks like this you have CSFI:
http://i561.photobucket.com/albums/s...CSFIEngine.jpg

I have the CMFI(top pic).

Could be a leaky fuel pressure regulator or "nut kit", (lines inside plenum) very common problem. Check fuel pressure and leakdown. Most auto parts stores rent and/or sell fuel pressure testers. Quick and easy test to determine if there is a leak somewhere. Ignition in RUN position, engine OFF, fuel pump running, pressure must be 55psi to 61psi and must remain above 50psi for 10 minutes after the pump shuts off. Check it a couple of times with both a cold and warm engine, and post your results.

Wouldn't it make sense for the mechanic to check the fuel pressure since he worked on the fuel system? Since he had it apart it would've made alot of sense. Could you tell that the regulator is leaking just by looking at it? He told me my old fuel pump was bad because it was low on pressure, so that's what tells me he tested it.

Absolutely you check the fuel pressure any time you work on fuel delivery! The regulator and/or lines can and do leak. In the early stages it can be difficult to visually detect, that's why you always check fuel pressure AND leakdown. If there's a leak, it will show up on a leakdown test. Provided he is aware of the test, the amount of allowable leakdown, knows how to do the test, and actually does it.... only HE knows the answer to that.

If it isn't the regulator, would it be possible to be a bad sensor? But....if it is, wouldn't it give a trouble code? Think maybe it might be a bad O2 sensor? I've owned this truck and I've never had to change a sensor, so that's a little suspect also.

If any of the sensors are bad, or circuit for a sensor, it will set a DTC. It is possible for an oxygen sensor to be "lazy" and not set a DTC though. Check fuel pressure and leakdown first. Very common to have problems in the plenum and it's quick, cheap, and easy to test.

Spoke to the mechanic and I told him the issues I'm having. He said everything has been changed that would affect those problems. He said something might have to be adjusted so it won't stall out, he said something about the tps--which I didn't know could be adjusted. I'll let you know how it turns out.

Simple to check it yourself for leakdown.
Check your receipt, see if it lists the injector, regulator and nut kit, (lines).

Could possibly be a dirty/faulty mass airflow sensor (located near air intake)

Hopefully it's something as simple and easy as that. He's still trying to figure out what might be causing the problem. I don't remember if I mentioned it in my earlier posts but sometimes the idle is erratic. Sometimes it goes low like it wants to stall out then surges to normal then lowers again, like it's hunting for the proper rpm's. Not all the time only sometimes. And it still sets no trouble codes.

The symptoms are similar to a faulty mass air flow sensor but, 1995 CMFI doesn't have one.

Just got a call from the mechanic. It was a bad temp sensor. It had no codes. I'll ask how he was able to figure it out. That's another $248 on top of the $1567 to get it running! I could've bought a 97 for $2000!
Hopefully it'll run for another few years with no more problems!
Thanks for all the help guys.

It's very possible for the ECT to be calibrated improperly and not set a DTC. As long as the ECT is not shorted out or open, and it sends data to the PCM that is within its normal range, no DTC will be set. The ECT sensor is the only data stream that the PCM has for determining coolant temperature. Easy test is when the engine is cold, first thing in the morning before starting the engine, compare ECT and ACT temperatures, they should be within 2 degrees of each other. At normal engine operating temp, the ECT should indicate ~200F.

yup it was the temp sensor. He said since we were having such warm weather--for Dec--the temps were somewhat close together, that's why the ecm never set a code. Pretty much what you just described!
You know your stuff buddy!:icon_worthy:

Thanks. Both ECT & ACT/IAT are thermistors. The resistance of the sensors changes with the temperature. On a cold start up, ambient temperature affects both sensors equally, no matter what the temperatrue is, which means they should both read the same. Don't let him pull the wool over your eyes about your warm December temps ;)

He does seem to know his stuff. Since I'm new to the area I went by word of mouth about his honesty(mother's:)). Now pricewise is another matter!
Thanks again Captain Hook! You the man!

I had the same problem with my 2000 4x4 blazer and found the transmission fluid to be very low and had a burnt color to it. Also, the cold air sensor had gone out. I had the tranny serviced and sensor replaced over a year ago and it's been running great every since.

For those who have a meter and want to check without using a scanner:
Attachment 38465

This should work on all temp sensors including IAT. I know it worked on Ford single terminal {for gauge} and dual terminal {ECT to PCM}

hey thanks for this info, for the ECT.