jwbeck17

Hi, friends. Had my '89 928 S4 at my local shop for an inspection and then the hurricane hit. The shop claims they got the cars stored away, but many suffered some impact from the water. They thought mine was ok until I went to pick it up and it would die upon starting. They kept if a few more days, tried to dry it out, and said it started fine. When I went to pick it up, it had the same issue, though I was able to get it running with the throttle. It idles very low and wills stall out until it warms up. Also noticed that when I rev the engine a little (around 2K) when cold, the tach is clearly hunting and pulsing. It stops hunting once warmed up (I gave it an hour drive today), but acceleration is weak at the lower RPMs.

The shop is suggesting that water may have gotten into the MAF (not sure how that happens). I'd rather ask you all from your experience.

Any thoughts on what may be going on here? Any suggestions oh how I should diagnose or address?

I have included two videos: one of the engine at cold idle after i got it warmed up enough to run on its own, and also one of the tach where you see where the idle is now (usually it is closer to 1K) and you can see and hear the hunting as I smoothly approached 2K on the throttle.

worf928

Is the IMS relay telling you anything?

Speedtoys

Did it get 'wet'..what does dry it out mean?

jwbeck17

Good suggestion. I didn't take a look at the panel, but will do so when I can. Driving it I feel like I have power (most likely not limp mode), however it has a some difficulty (almost a stutter) with harder acceleration for a second in the when the RPMs climb at first. After a second it seems back to normal throttle and fine at speed.

jwbeck17

I'm trying to figure out how did something tucked up high behind the engine and under the air filter mechanism got wet while waiting for a state inspection.

I suspect they were keeping the car outside for a few of the drier days to hope that any water evaporated. I doubt they put any amount of hours into it, honestly.

I don't think the car changed much since i originally went to pick it up and it stalled upon start (I didnt work the throttle then). I think they are grasping at theories of why it isn't starting easily anymore.

Thinking more to the car's repair history, a lot of problem areas have bene replaced.
- Fuel pumps an filters replaced 10000 mi ago
- Air filter replaced last year
- Spark plugs replaced a couple thousand miles ago
- Replaced a broken distributor cap about 5000 miles ago
- EZK/Computer replaced about 5 years ago
- I clean the grounds fairly regularly and replaced all fuses an old relays recently, (and it ran fine after)
- I have new spark plug wires ready to add as I was planning on doing it this summer

My current theory is that it just may be time to get a the MAF rebuilt and replace the distributor caps and rotors when I replace the spark plug wires (plugs should still be good). Also plan on replacing the hall sensor as it has seen better days.

I will check the IDM relay for a reading though.






All I can think is that

worf928

Yeah. Sense this doesn’t make unless there was a flood.

Bad recirc box seal might allow water to drip on the CEL or brain case.

Speedtoys

I would go the whole 9 yards.

Rebuild the MAF, an a whole intake refresh. It's not mentioned as done, and when it's all new at the same time, you dont piecemeal repairs every few years.

Something got wet, or touched while "drying" or...something. But something easy, once you do 10 other things.

worf928

Looking at your video...

I appears as if the TEMP-II sender has no weather boot on its connector. And - it's fuzzy - but it looks like a splice from the TEMP-II to the LH harness.

Electrical tape on the flappy solenoid connector.

There's also something strange on the LH harness as it exits from underneath the (broken) fuel rail cover.

It does though, look like an intake refresh was done at some point. When?

Download my inspection guide (URL in my signature) and go through the multi-meter electrical tests starting on page 22 section 8.2. After you disconnect the ECU plugs, check the pins for signs of corrosion, dampness etc. Then proceed with the tests. It takes less than 30 minutes and will help you rule-out/rule-in some obvious culprits. If you want to be stingy with the tests, do just the TEMP-II, Idle, and ISV.

FredR

First and easiest thing you might want to check is that your idle switch contact is functioning correctly.

linderpat

Also put the shop on notice that they will have a check to write. That is not acceptable!

jwbeck17

Thank you for your feedback and questions here, as I am very new when it comes to some of these checks and updates, but i can give you some better images and history under my care:

Temp 2 Sender and LH Harness: Below is a closeup pic. there is collar but no cover boot. I was not aware that there was one to be there. As for the tape and casing, that was my doing. the heat shielding around that part o the harness seemed brittle to me though function was fine. I added some additional shielding and sealed with self adhering vulcanized tape...rather poorly.


Flappy Solenoid Connector: FYI - this was serviced a few years ago (2017 I think) by Stan as my flappy was not functioning properly and he gave it an intake refresh. Connector has a full boot, but no tape (unless i am looking at the wrong area).



ADDITIONAL POINT OF NOTE: the front engine harness was replaced last year, as I finally installed the wiring I got from Sean.

I will most definitely look at your guide and review as soon as I get a free moment.

jwbeck17

I did just get some time to try to start the car and take a video of the computer area to look for an IMS green light. I did not see any indication of limp mode being triggered - no green light.

worf928

Ok. I see now that the TEMP-II does have it's rubber weather boot and the other 'visual' has been described.

My comment about 'tape' was the result of interpolating between pixels on the first picture. What has happened with your flappy is that the plastic connector's retaining tabs broke off and heat shrink was 'installed' across the connection to keep it from coming loose. Since a replacement connector is NLA (AFAIK) this is as good a fix as any if both retaining tabs snap off.

I did notice evidence of that and meant to point it out.

Idle switch and ISV are always the first thing to test if there are no other very-obvious items.

Since Sean did the intake refresh, baring infant mortality of a part, there shouldn't be any worries there.

Given the condition of the LH harness - as evidenced by the repairs - I'd have to put my money on 'harness.' There might be some 'spots' on the harness, that shouldn't be there but are due to age, where water can enter and muck stuff up. This could be as simple as one or more missing rubber gaskets inside the 2/3-pin connectors for injectors, Idle swtich, etc. to exposed copper where a harness branch takes a sharp bend.

Could also be another cracked distributor. Coil or plug wires with a break in the insulation(*).

Nevertheless the mutli-meter tests will at a minimum rule-out potential culprits and enable focus on other areas.

(*) Found this the other day on a clients car. Replaced with new. Made a slight difference in idle.

worf928

Was the 928 misbehaving at that point? And had it been running for at least 3-5 minutes?

jwbeck17

it was still misbehaving, though it is video of the cold start, so it hadn’t been running for 3-5 at that point. Would do it for longer, but another storm coming because, ya know...it’s 2020.