More no, no, no's and narrowing things down

[cyberman]

Alternator and tensioner will be on order today as soon as I decide what else to order.

Charged battery 100% started engine and INPA to see if I could figure out why I keep getting the ICV code-related high-idle trip. Cold, idle was 900, but as I sat there with the engine running, it slowly rose to 1200. Not good, so I tried a spare ICV and it changed nothing.

Observed MAF was reporting in INPA, but just for the hell of it, I disconnected it and the idle did drop a bit but was lumpy and idling.

Randy's said disconnecting the MAF proves nothing and I believe him, but just was curious.

Noticed the multiplicative adaption has continued to drop and it is at -9 now whereas additive is at 0.

So, I searched this forum and googled it. I found a few sources that said "extreme" negative adaptations point to a rich mixture. And, rich mixture can be caused by a failing fuel pressure regulator. It can also be caused by blockage in the fuel tank venting or blockage in the fuel return line. Of course a fuel pressure test at the rail would be the best diagnostic. But: it would cost about as much for a tester or for someone to perform the test as a new Bosch regulator costs (~$40 at FCP Euro) so I'm wondering if I should just throw it on my order. At 91K miles and an unknown history, why not?

One other thing, and I've been wondering about this all along: in the best of times (what passes for normal), I was seeing idle warm and hot at 840-850 RPM and I can't get a clear answer on what it should be. Numerous M44 threads give numbers closer to 750, with a rise of about 20 RPM when the AC is on. Since I was tracing down vacuum leaks and replacing the ICV, I just chalked it up to a small vacuum leak and, of course, it could be a tiny leak somewhere. But now that it's gotten much worse, well its confounding information. And, to further confound things, two issues appeared more or less simultaneously; a failed alternator and this.

Any thoughts? I'll take all the help I can get.

I wondered if one of the new injectors was pouring gas into a cylinder, but INPA smoothness wasn't that bad so I think we can rule that out.

I could get another smoke test, or do one myself, but I doubt a new vacuum leak just appeared and why would it go from 900 to 1200 RPM in a matter of minutes? Letting the engine cool down and repeating, it starts out at 900 and then goes to 1200.

Something seems to be failing somewhere, the question is WHERE?

[rf900rkw]

The fuel pressure gauge fitting is a standard schrader size; the same as like era Chevy's. Borrow a gauge from your local autoparts store.


What does the TPS read?

[cyberman]

The fuel pressure gauge fitting is a standard schrader size; the same as like era Chevy's. Borrow a gauge from your local autoparts store.
What does the TPS read?

Thanks, I know where the schrader valve is, it looks like I'd have to remove the upper manifold to reach it. So, just check with ignition on?

INPA: TPS reads 0.58 volts at idle. Is that high enough to throw off the system? I've been wondering, I thought it should be 0.5V.

[cyberman]

The sage continues, another day, more information leading to more questions and no solution yet. Cats are still alive. I checked that TPS voltage again off and on the car. As it sat, 0.58 volts. I removed it and found it varied from 0 to 5.1 volts across its range. But there is no easy way to adjust it. I found that I could rotate it slightly before tightening it down and get it to 0.51 volts. I contemplated drilling the two bolt holes out so I could rotate it more, but didn't try that since I don't know what it is supposed to be. I threw on the old BMW OEM part and it got down to 0.47 Volts, but there was no change in idle.

So, I started spraying carb cleaner around and noticed a drop in speed when I sprayed on around the bottom of the ICV. That has a new gasket, but it's been on and off several times in the course of this work. I'd ordered another J.I.C. so with nothing to lose, I sealed it with black RTV and confirmed the seal with the engine running, but that didn't change the 1200 RPM idle.

I have a new fuel pressure regulator on order. The part was on FCP Euro for $40 yesterday morning by gone and back-ordered by the time I returned in the evening to order it and the alternator and tensioner. But I found it on Partsgeek for $30, with no lifetime warranty. I pulled the vacuum hose off the fuel pump and idle jumped to 1400 but didn't think to block off the vacuum so didn't prove much.

One last thought: the check engine light was on when we returned from the last trip and it was the idle control valve (code 32) high limit. But it was barely noticeable while driving. So, since it was on empty, the last thing I did was fill it up and I accidentally overfilled it. The pump didn't automatically shut off and I was watching the pump for a while way past full, probably left a half-quart on the pavement and I did smell gas on the way home. Researching it, there are some claims that overfilling is a bad thing since the fuel can saturate the carbon canister back by the tank and either block it or the engine can suck in the vapors. So say that a one-time overfill can cure itself, but damage it in the long run if done repeatedly. Sort of makes sense that the -9 multiplicative adaptation indicating rich mixture would, maybe point to that except I only drove a 1/2 mile back from the gas station and at low speed. I don't think the multiplicative adaptions can mount that quickly.

So, this wild goose chase is going badly, the geese are running around and the cats won't help round them up.

[Vintage42]

The saga continues, another day, more information leading to more questions and no solution yet. Cats are still alive... So, this wild goose chase is going badly, the geese are running around and the cats won't help round them up.

Your saga is so knowledgeable and entertaining. What is it with Iowans?
https://writersworkshop.uiowa.edu

[cyberman]

Your saga is so knowledgeable and entertaining

Thanks, I assume someone else down the road may learn things. These cars, like us, aren't getting any younger and, as we all know, almost everything except whisky gets worse with age. I keep waiting and hoping one of the big guns around here will fire and point to the one thing I've overlooked. And, if not, once the new/rebuilt alternator is installed, I'll bring it down to the local indy shop and see if they can solve the issue. You'd think 1200 RPM is a big thing, easily solved... you'd think. I'm also wondering if driving it around a bit may clear out any saturation of the charcoal. But, I tried pinching off the vacuum load that goes to a little underhood canister which then goes back to the tank, and that did nothing. Inpa has an activation control for that and I did here the solenoid clicking. I also heard it for the DISA and a few other things, just to pique curiosity.

Oh, and now fooling around with INPA, I think I opened the ABS system (for bleeding?) and am getting a new error, 121 "height adjustment" and don't know how to close it. I'll have to disconnect the battery to put in the alternator, so that should do the trick.

[cyberman]

I'm still looking for suggestions, ideas and advice on this as I've run out of things I know about. It's been a real puzzle.

The alternator issue should be resolved as soon as Saturday, but the high idle issue is defeating me. Fallback is to take it to an indy shop here for diagnostics. I know it's hard to diagnose issues without being able to see and feel the engine, and just about every thread I've found on high idle points to vacuum leak when the OP bothers to update it with a final solution. In this case, I had good running for 500 miles or so after plugging every last leak and replacing all hoses and o-rings with the exception of the oil filter housing-engine which is weeping a bit and the squiggly small vacuum line to the vapor canister. That line looked good excepted frayed a bit on the end that plugs into the throttle body (highest heat zone) and I did put a clamp there and we've never seen any smoke coming from it. Below is a listing of my test results.

The loaner AutoZone fuel pressure test kit doesn't have a schrader adapter that fits. The Ford adapter included screws on to the fitting, but doesn't push down and release the valve. Since, I'll be getting my new regulator today, it may be moot. All other parts will be here by end of day, alternator, tensioner, etc. Today and tomorrow will be in the mid to hi 90's and my enthusiasm level has dropped enough that I'll wait for a temp drop on Saturday.

So, one last call for ideas on the high idle (900 cold 1200 when warm) and testing so far:

1. Throttle position sensor: I have several and all report approximately 0.5 +/- 0.08 volts (Inpa) at idle rising as expected as the throttle is open.
2. No drag or hangup on the throttle cables.
3. No vacuum leaks unless I sprung a new one recently but if so, I can't find it.
4. I have two new as well as the original and none of them affect the idle in any way.
5. Long term (multiplicative) adaptation is at -9 indicating a rich, rather than a lean fuel mixture.
6. Installed injections seem to be working fine, or at least uniformly as inpa roughness/smoothness is uniform at around 65-80 for all.

So, speculations:

1. The engine idles at about 900 RPM for a minute or so before quickly stepping up to about 1200+ RPM. It's almost as if a valve is opening and letting in more fuel or the DME decides on a new map, but contrary to that the short-term adaptions are at 0 (good, almost too good). Could this indicate an 02 sensor going bad? Also, I thought the canister solenoid in the engine compartment opened initially on start up and then closed after a minute or so. That would mean, assuming it's sucking fuel, that it should get less rather than more fuel. In any case, remember that initial idle is never less than 900 now and for as long as I've been monitoring it properly (Inpa) it's never been less than 840 and I think that too may be higher than normal, but, of course, maybe some remapping was done, or idle timing changed in the past as that was a dealer fix for rough idle.

2. Rich mixture: I overfilled the gas tank - could this having anything to do with it? Input reports high vacuum in the tank, off-scale, but there are a lot of things off-scale in Inpa. But contra indication for that is the -9 multiplicative could not have been changed significantly in the short drive ride home from the gas station. Also, I got the high idle code before I overfilled the tank.

3. With the alternator bad and running on battery, I'm not sure if voltages are incorrect, altering sensor readings. Of course, we can rule that out Saturday when I get the alternator replaced.

[Vintage42]

... The engine idles at about 900 RPM for a minute or so before quickly stepping up to about 1200+ RPM... initial idle is never less than 900 now and for as long as I've been monitoring it properly (Inpa) it's never been less than 840 and I think that too may be higher than normal...

My idle is ~840 at cold start, and upon return to garage with hot engine.

[cyberman]

Got too hot to finish the alternator install. Sidetracks included checking/testing the vapor recovery system and installing a new power steering reservoir, said reservoir causing more pain then I expected. Tomorrow promises much cooler temps so maybe I'll finish it up soon.

Checked fuel regulator and ordered another that will fit this time. Regulator diaphragm isn't broken, that's all I can tell. There also is no internal screen as there is in later model regulators.

Vapor recovery system: In the 96 model year, there is no carbon canister back by the fuel tank. Instead, there is a small canister with a solenoid (normally closed) on the driver's side fender wall. The solenoid is functioning properly and opens when voltage is applied. Otherwise, there is no vacuum leak when it's closed as a slightly fuel vapor loaded breath of suction told me, but only with power applied. Otherwise, the old hose is good. Coming from the fuel tank, there is a blue line with a fitting that tells me it was made to handle a little pressure and that goes into the top of the canister. On the bottom of the canister there is another vacuum line coming from the tank and it isn't secured well and is obviously for vacuum. The hose has a plastic female fitting that is made to fit over a small rubber sleeve which sits between the fitting and the male "barb" on the canister. The sleeve disintegrated and I have no idea where to get one, so I made do with some electrical tape and a hose clamp.

Otherwise, unless the new fuel pressure regulator fixes the issue, or by some miracle the new alternator does the trick. I'm still at a loss diagnosing and fixing the high idle.

Indy shop can test stuff and maybe repeat the smoke test, but that's all I can think of now.

Off topic, I had to take a hammer to the tensioner and bust it up. The reason was with too many ins and outs on that thing, one of the two allen-head bolts that fixes it to the engine stripped. Since I couldn't rotate the assembly out of the way thanks to the rounded T50 pulley bolt, the only recourse I had was to destroy it and I took some satisfaction in that. Once busted up, I could get my vice grips on that bolt head and break it loose.