Howdy -- new here so please forgive any naivete.

Truck has recently had weeks/months of erratic behavior. Hesitations, surges at idle, stalling irregularly, etc. Of course, when I took it in, the problem wasn't chronic enough so...... Shop eventually replaced the coil but problems continued. They've done me right so far but last week was a bear.

Truck went almost belly-up and when I (barely) got it into service, they replaced some fouled plugs and wires. Still ran badly and found that computer wasn't activating two of the injectors. Replaced computer but truck now runs rougher than before. Am told that I now need a new airflow sensor.

Quandary is this: truck idled okay (for the most part) before computer was installed. Now, suddenly, the idle is out of whack. Coincidence? Reaction to new computer?

Also, have heard of cleaning sensor wires with brake cleaner but am skittish about fragility of the wires. Truck has 145K miles on it. If I pull the sensor and blast the wires, are they just going to dissolve or snap? How sturdy are they? And where do I find a replacement for less than a king's ransom?

 

MAF sensor wire clean works for newer sensor but yours will probably not work. The sensor in your truck actually performs a self clean procedure that is designed to clean foreign material from sensing wires. Have never seen a failed or failing MAF in B-truck in many years. I know you trust the shop that you go to but it looks like they have replaced a LOT of parts but the problem is still evident. Did you have a new engine computer installed or a remaned unit. We have tried a number of remaned ecms at customer request and all have turned out to be a fail. Some make the truck run worse than before replace and some present different problems altogether. Did you have a check engine light on when having all of these problems and if so what were the codes output?

 

Never had the check engine light come on at all. At first, problems seemed to point to a vacuum leak of some sort. None found. Had had problems a year ago with a spark plug wire frying. The lurching was a little reminiscent of that so I was going to check that as well but everything happened before I could get to some time to look. In fact, the initial call from the shop was that plugs/wires needed replacement so that fit the profile. It was after that when everything hit the fan.

Could they have installed all this and not tuned or timed the new plugs? Seems unlikely but odder things happen in the world.

One thing: once it gets running and the idling is rough, if you pull the plug on the MAF, things even out. Reconnecting has to be fast or it stalls out. This is what I was shown when it was being explained that I'd need a new MAF.

Finally, when I start up after it's been sitting, it rumbles a little and conks out. When I restart, it rumbles again but seems to have just enough more to pull itself through. Almost like the first start "primes the pump" in a way. Back to the vacuum leak theory?

 

Have the engine thermosensor tested, could be causing a lean condition which you refer to. Next have the PCM ground tested.

 

Is this problem occuring all of the time or only at an idle? Do you feel a missfire like dropping a cylinder at idle and/or does the same thing when driving normal on road. ie poor accel and low power?. Trying to get a feel for what is happening as you drive truck. Was truck running great as usual and then this suddenly happened or was a gradual loss of power and idle stability experienced. The more info you can provide the more we have to go on in diagnose a remote problem.

 

Sorry to ***** your thread but it was close to the problem I am having.

I sought out this forum to try and get some info. I have a 92 B2600 with 150,000 miles on it. I bought it brand new in August of 92. I love the truck and it has been the best, most reliable vehicle I have ever owned. Recently, I changed the oil and the air filter. I keep the truck waxed and I get compliments on how nice it looks for the age all the time. After completing the service, I decided the engine bay was in need of detailing. I had not done it in a couple of years. I sprayed everything down with Simple Green and drove to the car wash. Now I know I am playing with fire here but I had done it in the past with good results so I opened the hood and while the engine was running, I sprayed it with soap and water. I did not spray the electronics directly but something got wet and it died. I dried everything off and it started right up but ran like it was only hitting on 2 or 3 cylinders. I got it home and dried everything again. Started it up and it ran like a champ.

Next morning, I start it up and drive about a 1/2 block and it dies. I push it back to the house and park it and take my car to work. Come home from work and pull the plug wires, distributor cap, etc and make sure everything is dry. I pulled off the air box and look to see if the MAF sensor was gummed up. Put it back together and drive it to work the next day with no problems. On the way home, it dies about a block down the street. Starts right back up and runs fine for about 10 miles at highway speeds and then dies. Starts right back up again. I am at a loss. It is an intermittent problem but I am not sure if it electrical or MAF related. Sorry for the dissertation but I thought someone here could give me a place to start instead of taking it to a mechanic and throw money at it.

 

I would be willing to bet that you did get some water in some place that truck does not like. Pull the dist cap again and look inside for signs of moisture. May have got some water down inside the distributor and now is evaporating and condensing again inside the cap.

 

I am convinced it is electrical in nature. It died yesterday after work. It was like the key was turned off, no sputtering or anything. The tach droped like all electrical had been cut. I tried to start immediately but would only turn over. I turned the key off and it immediately started back up and ran fine the whole way home. That is perplexing part, it is almost as if turning the key off allows it to reset and then will fire up. Could this be related to the ECU? Whatever the case, I am going to complete the tune up and see where I am after that. Thanks for the info guys.

 

If stalling as you describe then you are right. Water in the cap wll usually cause sputtering and then possible stall. Tach dropping off instantly like that is a good indication that you are loosing spark signal. Your ECU is to the right of the passenger footwell so unlikely you got it wet. I would start pulling connectors and drying with compressed air. Pay particular attention to things related to ECU power and input signals. MAF, main relay, coil, ignitor, etc. Don't forget about the crank sensor down below. It too is an important ECU input. Seems fairly obvious that problem originated with the cleaning so a good dry out should work.

 

I had a similar problem on my B 2200. It ended up being the ignition switch. If it stalls while you are driving, gently move the key forward and backward just a fraction. Be careful NOT to get into the "start" or "acc" detent. If it comes back to life - you have it. It took me awhile to find this but a new switch (without the key cylinder) fixed it.. Hope this helps