rossmatt06

I was on my way to work today and was running late so I only let my truck warm up for a minute or two. It started right away, went to high idle for a minute or two and then came down to 700 rpm the way it should. As I pulled out onto the main road and got up to speed the truck shut down as if I switched the ignition switch of. The truck is a manual so I left it in gear to see if the truck would pop back off. About ten seconds later it came back to life and ran fine the rest of the 15 mile drive to work. Any Ideas what it could be? I just replaced the TFI Module about a month ago (motorcraft part). I know the plugs and wires need replaced but the truck runs great after being warmed up. It only seems to happen when the truck is cold (right after comming off of fast idle).

Thanks in advance for the help!!!

dr_bowtie

check fuel pressure...

keep a spare spark plug with you...next time it does it pull off a wire and throw a plug in it and crank it over just to make sure it is spark related...

rossmatt06

The fuel pressure is 40 psi at the fuel rail. Good idea with the spark plug. The only problem is that it happens for a brief period (10 seconds). It didn't stall before I installed the new TFI module which was about a month or two ago. It just started doing it now that it got colder out (around mid 30s) and only shortly after start-up. I ran the KOEO and KOER codes and got 29 insufficient signal from speed sensor and 44 thermactor air injection system inop (right side). Would either of these cause my problems? Would the TFI module drop spark for 10 seconds while cold and pick back up?

wde3477

Year and engine may help to narrow things down a bit.

I don't think the fault codes you describe would cause the dropping out.

There should be a pickup coil inside the distributor - these sometimes get flaky before completely failing.

The TFI could have problems, even though it's relatively new. It's been my experience that electronics failures follow a 'bathtub' curve - increased failure rates when relatively new, followed by a long period of few failures, ending up with increasing failure rates as the parts reach the end-of-lifespan.

There are resistance checks that can be performed on the TFI, pickup coil, and ignition coil - most any shop manual should have the specs. Not the end-all-be-all of definitive troubleshooting, but a good place to start.

Your events strongly suggest an ignition problem - but keep other possible gremlins such as a bad / flaky ground, a computer issue, and the like in the back of your mind.

Good luck, and keep us posted!

rossmatt06

Thanks for the input! I've been doing a lot of searching on the web for possible solutions and have found a few forums with issues identical to mine but no mention on how it was resolved. I haven't purchased an service manual yet but I think I will have AutoZone order me a Chilton manual this week. The truck is a 1990 F150 with a 302 and 121,000 on the clock. I have a new pickup coil from that I was going to drop in friday night but ran into problems getting the gear off of the bottom of the distributor and gave up before I broke it. I cleaned the grounds on the distributor and made sure everything was tight. I noticed after I re-installed it in the truck and timed it that it seemed to run better than before but don't know if it fixed (or temporarily fixed) the issue. It started and ran fine this morning with the temp at 24*F. I'll keep my fingers crossed that it was a simple ground problem and will let you in on my findings with the tests on the TFI, Pickup Coil, and Ignition Coil. Thanks again for your help!

farmer12

I had a very similar prob just yesterday with my 89 5.8. Drove it to town to help move a friend an after we were all done loadin it wouldn't start...no spark. Went and bought a new coil thinking that might be it, an it fired up. Got to the other place got done unloading and went to leave....dead again, no spark. Put a new ignition module on and haven't had a prob since. It is possible you got a bad module. I had just recently put a diff module in mine. Worth a try.

rossmatt06

It's been about a week since I tried to replace the pickup coil and failed. The truck has been running extremely well until this morning when it exhibited the same problem. It was very damp this morning so I am beginning to think it's a cold/damp only issue. The truck started right up and went to high idle, then came down off of high idle and shut right off. I noticed the tach went to zero as soon as the engine shut down but before it really reached zero RPM. Once the engine was fully stopped the tach jumped up to about 300 rpm and immediately returned to zero. I restarted the truck and it again shut right down. I had to crank the truck a few seconds before it finally started the third time and it ran fine the rest of the day. I heard that spraying the inside of the dist cap with WD-40 would help dissipate moisture but that didn't seem like a very good idea. Would moisture in the dist cause this kind of problem? Any other thoughts?

wde3477

My experience with moisture in the cap is that the truck will misfire and otherwise run erratically. WD40 will work, as will just leaving the cap off to let things air dry. I usually run into this problem after hosing the engine off.

Replacing the stator pick-up is challenging - the distributor shaft must be spotlessly clean, and the varnish must be completely removed. For the trouble and the likelihood of breaking the gear - suggest to consider buying a replacement distributor with the pickup already installed. If that's not feasible - be careful, the gear will break if forced too hard. Be sure that the gear pin has been removed.

Suggest to get those resistance checks - may find the problem isn't with the pick-up.

ymeski56

I once caught one of the small wires to the coil underneath the the distributor cap during a replacement. It had gotten doubled over & smashed pretty thoroughly. It didn't cause me any problems until I discovered it & straitened it out. When I did that, the wire started to separate inside the insulation. It looked ok visually but started dropping out the coil w/ more & more frequency. I finally found the culprit by wiggling wires while the engine was idling. Something else to consider. Also, my neighbors truck was pulling the same crap for 2 months. No particular pattern. I thought maybe TFI but they're usually good for a couple or death rattles and then fail completely. So he took it to a Shop (actually shop #3, he started at the dealer,they tried to tell him it was the Charcoal Canister) and they made him leave it for a week. A week later & $400. poorer, they gave it back to him w/ a new fuel pump installed. 3 week w/his fingers crossed, still no problems! You have my condolences, intermittent problems can be a royal pain!

rossmatt06

I finally got around to purchasing a Haynes Repair Manual today. Here are my findings from the resistance tests... The primary ignition coil was .4 ohms which is in spec. The secondary coil resistance was 2.686K ohm which is well below the 8K to 11.5K suggested values. So possibility #1 is the coil. The second test on the PIP Stator showed a constant 7.4 VAC as well as the SPOUT which was 7.4 VAC also. Both within spec. The last test was on the TIF module itself. All of the readings were well within limits except for the last one which was PIP Pwr to PIP In with a reading of 761 ohms. The listed range was between 900 ohms and 1500 ohms. I tested the old TFI module that did not exhibit the startup then stall symptom and it to was around 761 ohms. So my next question is would a bad ignition coil cause these symtoms?

Edit: I found resistance values at http://www.therangerstation.com/tech...iagnostic.html and the PIP Pwr to PIP In resistance was rated less than 2000 ohms. Mine is 761 ohms so that supports my assumption (I know it's not good to assume) that my new TFI module is ok.