wednsday while going home, it started, BAD buck at 4000 and the engine almost quit on me. thought nothing oof it till it did it again 1/4 mile down the road at the same RPM. went home and threw the scanner on it and pulled codes 33 34 35 and 42 and the engine said it was at 50 deg advance @ 1500. that's way too high. no SES at this time, so i adjusted the timing down w/ the scanner to a more sensable 18 deg @ idle (couldn't go lower) and then the SES came on. now there's a bad miss @ 1500 only and then the engine quits @ 4000.

any idea as to what that may be? new plugs, wires, ign modual (tested before install), MAP, pick-up coil (tested before install) and IAC valve

need some educated guesses here cuz i'm stumped
thanks,
Arty

You did'nt state what engine you have but the scanner showes total advance. The best way to check timing is follow the under hood decal and use a timing light.

Ok, start out by setting your timing using the proper procedure. Ground the diagnostic pin in the ALDL connector to the ground pin right next to it, this sets the ECM timing control into bypass mode, then adjust the timing to the value listed on the VECI label, should be 10° or thereabouts. Once this is done and verified remove the ALDL terminal ground. The ECM commands over 30° of advance at idle, and has a fairly complex, nonlinear timing curve programmed into it.

Next, reset your ECM by removing power for a couple of minutes, then reconnect it. Restart your car and drive it around a little bit, then pull the trouble codes again and see which ones are current. The ECM remembers trouble codes long after they are initially set.

The first two codes you report indicate a problem with the MAP sensor, or more likely the vacuum lines to the MAP sensor. Thoroughly inspect the vacuum lines for cracks and decomposed rubber fittings. The high idle is indicative of a vacuum leak, and the fact that the ECM couldn't control the idle with the IAC would probably account for the code 35. Code 42 usually indicates a module problem.

My bet's a major vacuum leak. If you have the V6 check the EGR tube where it goes into the plenum. And to repeat, be very thorough when checking the vacuum lines, especially the one that goes to the MAP sensor and fuel pressure regulator (assuming you have the V6.)
JazzMan

well it's the 2.8 and there was no warning for this onslaught of crap that i'm getting from the engine, it just happened (poof). as for the timing, it was set correctly and locked down months ago when i replaced the wires and plugs so i'm fairly sure it isn't a physical thing. today i replace the ign modual, cap and rotor, and wires (they were arcing) and still it won't rev past 4000, but the buck at 1500 went away.

also i noticed during the drive home, the scanner was reading a constant ~30 deg but when i put my foot into it the timing droped to as low as 9 BTDC and the TPS voltage was at 0.33v at idle ( i know it should read about 0.5 at idle but it's been good for so long i let well enough alone) noticed slight arcing at the coil but i've seen MUCH worse and the car ran fine.

i asked one of my instructors and he indicated a possible faulty pick-up coil so i tested that and came up w/ 815 ohms which seems about right. as for the code 35 , i think it's BS b/c the engine idles just fine (no searching). checked the plugs and the indicated a lean condition but i know it's running rich so it's definately too advanced timing though not bad enough to warant concern. i hope its not a faulty ECM cuz that would just suck.

one other question: would a leaking donut cause an O2 sensor to read a lean condition or is that far enough down stream to not affect it?

PS: it's not a vacuum leak at the EGR tube, it's brand new and pressure tested plus there's no high idle accept during warm-up (normal) so that's out.

[This message has been edited by fieroman87 (edited 05-21-2005).]

Check to see that you didn't lose a bank of injectors because of a faulty connector. Mine had problems and lost power for the same reason. The connector which caused me problems was located by the thermostat housing.

The reason I said to readjust your timing is because you yourself said that you "adjusted the timing down w/ the scanner to a more sensable 18 deg". Did you adjust it by turning the distributor? Unless you burned a new prom for the ECM there's no other way to adjust the timing on your engine besides turning the distributor.
If you actually did that, then you need to readjust the distributor to the proper setting before proceeding. If the timing is off then there's nothing more to be done here until it's verified as being correct.

JazzMan

ok, who want's to put money down on it being a streched timing chain? any takers?

we'll find out for sure on saturday....stay tuned

Arty

quote Originally posted by fieroman87: ok, who want's to put money down on it being a streched timing chain? any takers? we'll find out for sure on saturday....stay tuned Arty

Not me. Too many backwoods hillbilly idiots fail to properly diagnose a driveability problem, claim the engine "jumped time", and rip it apart. These are the cars that never get put back together and litter the midwest's landscape. How many times have timing chains been a problem in the last say, 5 years and 16 cars I have had, some of which have been abused, neglected, and over 200K? None. Timing chains are the scapegoat for the common man's lack of intelligence, patience and diagnostic skill. As you can tell, this is a bit of a pet peeve of mine. I am currently converting a 1992 Cavalier 2.2 5 speed for operation on propane, but with vapor phase injection, as opposed to the common liquid phase injection or vapor phase carburetion. I got the car for a couple hundred bucks since it didn't run. Spark but no fuel. ECM was in fact grounding injectors, and there was fuel pressure. Overlookers as I fixed the car speculated that certainly the vehicle did not run because the engine had "jumped time", and one suggested that I had broken a timing belt, since "all four cylinder engines have them". After diagnostic work I found the real source of the no-start condition; an injector had shorted to 1 ohm of resistance when the nominal is 12 ohms. Most of the power went through the path of least resistance and since the injectors are parallel and MPFI, none got fired. Point of the story, is that slack timing chains do not cause an intermittent miss

As Jazzman said, I am curious how you adjusted the timing. Also it seems like writing on the wall to have both a MAP code and a high idle code. Recheck those vacuum lines, spraying starter fluid around every vacuum line and gasketed mating surface having to do with the intake, including the EGR.

Kurt

You didnt mention ignition coil, battery connections, clogged fuel filter, or just bad batch of gas. If you have a vacum gauge, see what its doing. You should be able to get like 16 inches of vacum at idle or lower steady rpm. If not you may have a vacum leak or leaking cylinder head valves.

Save some time , re-adjust your timing at the distributor first , then track down or eliminate your problems from there.

this is why i said we'll find out on saturday.... i'm just going to verify that it is NOT the chain, that's all. don't plan on tearing anything apart just yet.

PS: I just verified base timing as perscribed by Jazzman and it turns out that it was WAY retarded (over 10 deg), so i adjusted it by the book (jump ALDL to ground). unfortunately it didn't fix the problem, the engine falls on it's face at exactly 4000 (still) and if i try to push any harder, it quits on me. there are no vaccum leaks, and the IAC valve is opperating normaly. at this point in time, the engine won't even fire up (does turn over).

so now what?

[This message has been edited by fieroman87 (edited 05-27-2005).]

here's a new sugestion i was reciently given: possible faulty ECM. any oppinions on this?

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Arty: a.k.a. FestYboy or Fieroman87
'87 GT 5 spd. '88 Festiva 5 spd. '87 Scirocco 5 spd.
Yahoo messanger: AMAbonus
AIM: FestYboy88L

I've seen a distributor lock up the release and actually change the physical timing. Checking the distributor is good advice.

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If it don't fit force it. If it Breaks it needed replacing anyway!!

Arty, To rule out the timing chain deal, use a ratchet and turn the crank a few times , then listen, if the car starts you`ll hear it big time... Yes a new/bad ecm could cause all kinda things to happen, do you have a extra one that fits your application??? If not let me know, I have a 86GT 2.8 automatic trans ecm sitting here I`d be glad to ship over for you to use , to see if its the problem. When your done , please ship it back, hell I may need it , I just finished a 2.8 build this winter.... Sound like a plan???? Let me know. Hope this helps out some. Jeff

quote Originally posted by fieroman87: ok, who want's to put money down on it being a streched timing chain? any takers? we'll find out for sure on saturday....stay tuned Arty

You can find that out in like 5 min. just try to turn it back and fourth by hand. sloppy? bad timing chain. Is it the problem? No.

quote Originally posted by HellYes: You can find that out in like 5 min. just try to turn it back and fourth by hand. sloppy? bad timing chain. Is it the problem? No.

how not?

ok it's NOT the timing chain, or ECM so all i have left is the distributor. what (other than electronics) could fail in the distributor that you CAN'T see by taking off the cap?

quote Originally posted by fieroman87: ok it's NOT the timing chain, or ECM so all i have left is the distributor. what (other than electronics) could fail in the distributor that you CAN'T see by taking off the cap?

Rebuilding the distributor is not a big deal or very expensive for that matter. With a little mechanical ability and an hour to kill it can be done by just about anyone. I was terrified of pulling my distributor to rebuild it but it turned out to be a fun project. Just make sure you get the gear back in the right place. It can only go on 2 ways but it's marked so just pay attention to how it is lined up when you take it apart.

well this will be the third time i rebuild it so doing it's not a big thing for me but what is a big deal is finding out what is causing the problem. this is where i get hung up. i've replaced all the electronics in the distributor and all test good so it's now down to a physical problem as far as i can tell.

i'm up for sugestions

Problem solved, it was the primary power wire to the coil. high resistance and poor connection caused all my woes.

NOTE, this is the second time that wire has failed on me so consider it a common failure!!!!

Arty

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Arty: a.k.a. FestYboy or Fieroman87
'87 GT 5 spd. '88 Festiva 5 spd. '87 Scirocco 5 spd.
Yahoo messanger: AMAbonus
AIM: FestYboy88L

Hey i'm having the stumbling at idle and 4000rpm cutoff problem exactly as you described in a thread....

which power cable was it that was causing this for you?? was it the actual spark plug type wire that goes from the coil to the center of the distributor, or was it a smaller cable running in through one of the connectors to the ECM???

Very curious to know, this has been baffling me like none other, i'm wicked off on timing at idle and at about 4k rpm it just dies out .... odd engine noise, gets a lot louder.

Backyard mechanic myself, never took any courses, so I just shut the car off and it's pretty much been sitting there for the last year with the occasional once a month my starting it scratching my head some more and shutting it off.

I've thrown an entire new distributor (all parts 100% new), new set of plugs and wires, full exhaust cat-back (including the cat itself), new MAP and TPS sensors, and new vacuum tubes all round (these were all solutions 3 diff local shops gave me...the catalytic made 0000 sense to me, but I had an ocelot exhaust I had never installed so I figured it was as good as time as any to do the full exhaust.

Anyhow, if you found a solution and could describe to me exactly what wire you found doing it, that would rock....... I'd owe you a beer or 6