This is turning into a very long saga, but here's a short version

Car starts and idles ok-ish, but idle jumps a bit about 500rpms to 800rpms, occasionally stalls but not often. If you attempt to drive it then you have no power, it doesn't rev past 2k, you can have your foot 50% throttle or more and it just sits at 1k rpms then backfires (I think through intake not exhaust) and car lurches forward since rpms go to 2k , then back to 1k and rinse/repeat, going up a hill is nearly impossible

odd thing is that about after half a mile and one of these backfires it's just fine, all of a sudden you feel you have more power and you can redline it if needed and it pulls hard as it used to :shrug:

It may coincide with the "service" light going off, but I have not confirmed that yet. Speaking of that light, what does it mean vs check engine?

- it does not have anything to do with engine being cold, I can let it idle badly for an hour, temp gauge in mid & heat in cabin and it will still do this

- it doesn't fix itself idling, only when being driven ala uncle buck backfiring/stumbling down the street

- new plugs/wires/coil/cap/rotor
- another MAF, both do this
- fuel pressure at around 40psi even when stumbling
- no vacuum leaks , all hoses have clamps now, I even used smoke machine to find any small leaks left
- new intake manifold gasket
- new TB gasket
- cleaned IAC
- cleaned TB
- cleaned EGR valve (worked when vacuum was applied)
- readjusted TPS - seems ok (hard to tell)
- replaced in-tank fuel pump (I think I misdiagnosed something earlier).
- checked timing belt, seems ok and not old/chafed or anything like that
- new PCV setup, new flametrap, new hoses, new oil separator

I don't seem to have a lot of suction on the oil cap, not sure why or what it may mean, but if I Put the cap on loosely it doesn't suck it down as some FAQ doc suggested it should :shrug:

When it's stumbling if I unplug MAF the revs even out and no more surging, but it's hardly driveable without a MAF , I believe it suggests that MAF Is ok since things "Change"

What controls timing on these cars???

Since it somehow fixes itself it has to be some module or electronic component right? I suspected a lot of things, even headgasket but after pulling intake off and checking oil there are no signs of that going bad.

Any ideas would be greatly appreciated.

 

Lots of more people with more experience will chime in... however... I'd start with the MAF. It is important that LH 2.2 and 2.4 used different MAFs, and they are not interchangeable. Not all people (like you went to an autoparts store and they helped you get it) are aware of this. Then there is Lh 3.1, and I know nothing about that and the regina system. First, I think we need to establish what system yours uses. I'd think it's LH 2.4, but I don't know.

Timing is controlled electronically, I think it's called the EZK.

When the system isn't getting correct readings, it goes into "limp home mode." that is what you are getting when you disconnect the MAF. Since it changes when you don't have the MAF hooked up but goes back to not working properly when the MAF is hooked up again, I'd re-examine that.

That's my two cents.

 

I thought I'd read somewhere that the way to test the MAF is to unplug yours and if RPMs visibly change it was likely working ok (crude test I guess).

The spare one I got was used from '89 740 I think, it's the 6 wire version I have the bosch ignition, but either my stock '94 or this one cause the same behavior.

tapping on the MAF does nothing (I Had some where this would cause "change" before in other cars).

I'm not ruling MAF out as you said, but I am also tired of buying parts and what's the chance of 2 being broken in the same way... :shrug:

 

Just a note - you should never plug/unplug the MAF while the engine is running. However, if it runs and idles better without the MAF then it is suspected to be faulty.

The Service Engine light is not the same as Check Engine. Service light goes on every service interval (7500 miles or something like that). It can be reset using the recessed button in the corner of your instrument cluster.

 

Dimes to donuts your plug wire replaces are wrong. They may be oem but they are incorrect. I had the same issue and replaced everything you have. I went to this guy at collins repair in rock hill, sc. The guy says he just replaced the plug wires. not a single problem since. I didn't believehim but he said it's that they are super sensitive to those wires. So maybe a call to him to see which are best. I'm telling you, not a SINGLE problem after her put HIS set on.

 

the *ONLY* plug wires I'll put on a red brick are the Bougicord sets as sold by fcpeuro, ipdusa, etc.

 

Just ten days ago we purchased a 1984 245 wagon (B23F) AW70 E/OD tranny. Have cleaned MAF, Idle Air Control Valve and throttle body (like second day we had it-cleaned up a rough idle very nicely). Have driven it about 650 miles back and forth to work in the next town over and has been trouble-free (well, after hearing a groan and a shriek last Friday night, I've replaced both front wheel bearing sets and changed the gear lube in the (open) differential - the noise has not returned. Have not yet changed plugs, plug wires, distributer cap or rotor, but plan to as P.M. next payday. HOWEVER; this morning coming back to our little burg, Truckster suddenly lost power and, when giving it accelerator, it would, for just a split second (really, less than a second) pick up RPM, then return to a dead pedal... Pulled over on the highway and it had a very high RPM (no tach, but guessing 1500 - 1800 RPM). Shut if off and restarted. Started easily and cleanly and off we go, only to have it happen again within about 4 miles. Same thing, very high idle (enough to travel probably 10-15 MPH) but this time I had to crank for 15 seconds on a couple different attempts to get it re-started. I'm quick to cast blame on the injection ECU since it almost seems like it enters into a "limp home" mode with the high idle. Just now going to start trying to diagnose, but know it's going to be difficult based on the intermittency of the problem.... Anybody had this experience??? Oooooops, forgot... It has 214,000 miles on the clock.

 

air leaks in the intake path are the #1 cause of that sort of thing. Unless you have one of the few problematic ECU versions, they are generally ROCK solid reliable... our 1987 has about 500k miles on the original engine.

now, your car IS in the window for 'biodegradable insulation' ;-/ this is approximately 82 to mid 87 (ours is late 87 and dodged it). on these cars, the wiring insulation becomes brittle with age and heat and eventually starts cracking and flaking off. it does this inside the black tubes so you can't necessarily see it. when this happens, all SORTS of annoyingly erratic problems start happening.

 

Thanks for that Pierce! It may well be a wiring gremlin, I drove it to work and back again this afternoon (about a 24 mile round-trip jaunt) and nary a problem! Faulty wiring is really the only thing that makes sense given this is such an intermittent problem. While home, I did unplug the ECU and spray the connections with contact cleaner.... and stopped by our local NAPA (only auto parts around our little burg) and ordered a fuel filter (which I need to replace as P.M. any way-no idea how old the current one is. We'll see what develops over the next few days!

 

I'm not sure I've *EVER* had to replace the fuel filter on any of our volvos.. the only one we bought new has about 500K miles on it now. I did have a mechanic replace the main fuel pump a few years ago when it went erratic and I was too busy with $job to deal with it myself... he may have done the filter too.

 

In 40+ years of car business related fields I have replaced 2 fuel filters (on others insistence), and it made no difference. Not saying that a fuel filter never goes bad, only that very, very rarely, usually due to some contamination or car sitting for years with bad gas will a FF be in need of change. The symptom of a clogged filter is fuel starvation under heavy load; other than that, you are throwing money away--when clueless about a problem, it's one of the easy things that comes to mind to do...

 

The new fuel filter did it! Truckster no longer loses power while driving down the highway - it still has an intermittent high idle, but I'm no longer worried it will suddenly lose power and die along the side of the road. There is no telling how old the fuel filter was, the P.O. didn't say anything about changing it in the three + years he owned it. Still checking for any manifold air leaks or vacuum leaks which might cause the random high idle situation-of course this might turn out to be the wiring harness gremlins Time and further poking around the wiring will tell!