sc4ram

I spent most of the afternoon today at the side of the road (actually a parking lot) . The car was motoring fine then suddenly the check-engine light appeared and the engine cut off, the light went off and the engine resumed operation and so-on and so-forth. This happens in a ~1 second intervals. Now in "try to limp back home" mode, I removed the positive cable from the battery and grounded it out for a few seconds (hoping it would reset the Control Module if that was the problem) . The car then ran ok, until i took it for a ride around the parking lot and it started cutting out again. Thinking it may be heat related, I let it set for a hour and walked down the road to have lunch. Upon return the car acted the same way. In desperation i pulled a spare coil out of the back and connected it, the car started and ran fine. I drove it down the road about a mile and it started cutting out again. I then had the car hauled home, and dumped in the driveway, now I cant get it running long enough (out of this oscillating "cut-out" mode) to pull into the garage. Any clues folks??? (not that this would be related but about 2 weeks ago, it blew a "gauges" fuse that happened to be inline to the AC clutch relay, I replaced it and the AC has worked fine since then. )

sc4ram

Well, after letting the car sit over night (after several failed attempts trying to get the car to run normally yesterday) outside with the battery cable disconnected, I started it up this morning . It immediately defaulted to the run-stall oscillation . I fed it some throttle and suddenly it ran normally. I was able to turn it around and pull it into the garage.

Presumably I'll be able to repeat this problem. Any clues how to diagnose it if I do??

OrangeBird

iTrader: (1)

Just like any other engine that won't run , your loosing one of three things , fuel , spark , or compression . Since it runs & quits you can pretty much rule out compression , leaving either fuel or spark as the cause of the chronic stalling .

Were this mine to diagnose first thing I'd do would be a fuel pressure test , followed by a noid light check of the injectors , with a test light check of the +12V feeding the ignition coil thrown in for good measure . Also , you mention the check engine light coming on , did you do the paperclip trick to read any stored codes ?

sc4ram

Thank you , all good places to start. Just some more background, the check engine light has come on briefly for decades and goes off either during driving or after shut/cool down. It seems to be coincident to the engine reaching full temp on a hot day. I just watched the "paper-clip" code-pulling video, I'll give it a try once I can replicate the aforementioned condition. (Something to work on during Turkey day) Happy Thanksgiving!

sc4ram

I've made some progress. Up till now I couldn't replicate the failure , Id let the car idle in the back yard for a half hour at a time and it ran ok, then Id pull it back into the garage. I pulled the MAF and cleaned it and installed a new fuel filter. Today I decided to take it for a run and try to make it fail. Fortunately I stayed in my neighborhood and within a short distance of my house, while driving the check engine light came on and the engine started misfiring again (barely running) , I was able to limp it back home to the garage. I immediately pulled the code and it was Code 33 (MAF), (I replaced a bad MAF decades ago, i seem to remember it would run poorly but it would run good enough to drive it to a shop, it wouldn't of made it today) . The car is in solid failure mode now. (although I'll bet if I messed with it, pulled bat cable etc I could get it to run normally) . It wont start but it will fire. If I pull the MAF connector or the Temp sensor connector it wont fire at all. Ive been reading the great threads here. The wiring is in great shape. I will check the relays and wiring continuity anyway per the decision tree https://www.thirdgen.org/forums/tpi/...de-33-maf.html If i kick those things around and dont find any issues, it may be time for a new MAF.

sc4ram

Well, seemingly good news here. I eliminated the Mass Airflow Sensor (MAF) relay, the wiring and the fuse as a probable cause by testing/continuity. At that point last week I ordered a el-cheapo MAF from AZ ($52, beats paying flat-rate hours for trouble shooting) . It arrived today and I popped it in . The car started and the check engine light went away. It idled rough, and I had to adjust the idle upward a few times so it would stay running with my foot off the gas (it acted like it had self reduced the idle speed) . As the engine warmed up and after each time I stopped and started it, it ran smoother. I'll give it a test drive tomorrow (in daylight in case it dies) , but if the trend continues, its running noticeably better than before the original problem occurred. (including not running as rich)

Given all of the poor reviews Ive read here on MAFs (especially cheap ones) Im considering buying a top shelf one (either Delco or some other high-performance product,) and carry this one (AZ) in the back as a spare so this issue doesn't strand me again . Then again if it is running fine, why not buy another $52 one (+$5 for core) and throw it in the back (gently) for a spare. The Delco MAF I previously installed lasted decades.

Any thoughts?

sc4ram

Just another thing I've learned about the MAF, a mechanic told me if the car was dead on the side of the road and I suspected the MAF, unplug the MAF and the car will operate to default settings. I had the car cut out on me a while back (acted like it would if the MAF was going bad) . I parked it, unplugged the MAF, went to lunch. Came back and it ran sufficiently to get me back home. I eventually plugged the MAF back in , and the car ran normally. (I carry a MAF spare now) .........