Swapped M20B25 stumbles BADLY. Assistance, please

[phenryiv1]

I swapped an M20B25 into my 87 eta car in prep for this rallycross season. The season starts SUNDAY with a test & tune tomorroew. As of now...not looking good.

This post will be long- I want all of the info out there.

Current situation:

After several days of letting it run (now that the cooling system is installed and bled), the car starts up fairly well but idling is a little rough. Not terrible, but not great. It stumbles badly when I put it under load and it has absolutley no power. It feels worse than the eta motor, and I could barely get it to stay running long enough to pull it into the garage on Wednesday to put it up on the lift to do the exhaust. I don't have a working tach right now but it does not feel like it is revving very hard or very far.

Backstory:

• B27 had a bad oil leak so we swapped it out.
• THe B27 was fully functional, but...
• The external fuel pump was LOUD at times. Functional, but loud.
• B25 was bought from a R3v member who was doing an M50 swap. I was initially under the impression that he had built the motor, but I came to find out that he bought it from someone who had refreshed it. The motor looked really clean, but I started to find a LOT of RTV on things...particularly intake/vacuum hoses in the TB. It was also missing the CCV hose (VC to TB)- more on that later.
• I was also told that the motor was stock, the timing had been set, and the valves were adjusted. HAVE NOT VERIFIED ANY OF THIS.
• I am on a stock 173 DME.
• The exhaust was removed to go to a single 2.5" exhaust w/o a cat (car is track/rallycross ONLY and is towed to events). Re-installation of the exhaust is still ongoing as of the time of this post.
• Right after the swap, we started it up and had a C101 issue due to the presence of airbag wiring, but that was resolved.
• I had an early model radiator and a late model water pump, so I had to run the car sparingly when we first fired it up.
• Gauge cluster was always somewhat irregular in the eta, but after swapping in the 2.5 the gaiges seem to be very erratic. Temp gauge is bouncy, fuel gauge seems right, tach not functional (a 7K tach was swapped into the eta cluster).

So after starting it up, the car idled okay but with no exhaust, it is LOUD. I have completed the exhaust path but have not permanently installed the parts. Hopefully, I can do that today.

I FINALLY got in the missing CCV hose last night and had high hopes that the stumbling under throttle woudl be resolved. No such luck. I am pretty much at my wits end here.

Diagnostics/ Trial & Error:

Here is what all I have tried, as well as the result:

• Bypassed the ICV (sealed off both ports and used my foot or hand to hold throttle to replicate idle): Did not seem to make a difference.
• Installed the new CCV hose. No real change to the stumbling. Idle seemed to be better/worse from one startup to the next and had no consistency.
• Stomp test: no response (cluster is an 87 eta cluster with a swapped tach)
• Swapped DMEs for another stock 173: no change.
• Disconnected AFM: idle slowed, recovered.
• Reconnected AFM: idle slowed, recovered.
• Disconnected ICV: no change.
• Reconnected ICV: idle slowed, recovered.
• Removed speark plug wires: Each time the motor stumbled and recovered, but on the front one removal caused a stall every time I disconnected it.

Pretty much down to the piss-poor diagnostic concept of replacing intake/sensor/fuel parts 1 at a time to checking for a change. Looking first at the AFM, ICV, TPS...easy stuff.

I plan to try to check injector function after work, and then to check that the spark plug wires are on the car in the proper order. Another suggestion to check is fuel pressure, but I don't have a FP gauge. There is a chance that the fuel pump was damaged or simply died during the swap process (or that the heat from the welding/install of my roll cage somehow damaged it), but I can't SEE any damage and it is at least partially functional.

Where should I go next with diagnostics?

[jlevie]

Are you using the AFM for an M20B25, or the one from your M20B27 engine? You need to be using the correct AFM.

Did you "smoke the harness" from pin 20 of C101 being grounded? If so, there can be more damage in the harness than is evident. You may need another harness. If using a late engine harness, make sure that C191 is good.

With the correct AFM and a good harness, the next steps would be to verify cam timing, run a smoke test, and check rail fuel pressure. If the engine had sat for a good while, have the injectors cleaned and flow tested.

[gtdragon980]

I would check the c191 as well. Mine was so corroded that it caused stumbling, misfires, etc. Bought new pins from the dealer and rebuilt the connector and have not had a problem since.

[phenryiv1]

Are you using the AFM for an M20B25, or the one from your M20B27 engine? You need to be using the correct AFM.

AFM, ICV, etc. are all from the '90 "i" car, so they are correct. Not 100% confident that tey all are working, however.

Did you "smoke the harness" from pin 20 of C101 being grounded? If so, there can be more damage in the harness than is evident. You may need another harness. If using a late engine harness, make sure that C191 is good.

I THINK it was pin 20, and yes, it smoked (in the ground point behind/above/left of the steering wheel (thank God the dash was out!!!). I was hoping that it only killed the DME so I swapped DMEs to no avail.

What else might I have burned, and where? I con't have another harness, but if I have to buy one, I have to buy one.

Harness was a '90 harness so I assume it was late model. Might I try to source an '87 harness to simplify things? Will an '87 "i" harness work with a '90 "i" motor? Would my '87 eta harness (still a Motronic...) work on the "i" motor?

With the correct AFM and a good harness, the next steps would be to verify cam timing, run a smoke test, and check rail fuel pressure. If the engine had sat for a good while, have the injectors cleaned and flow tested.

Motor had not sat prior to me getting it. It was run within the last few weeks.

I am looking to check FP tonight or tomorrow.

[phenryiv1]

I would check the c191 as well. Mine was so corroded that it caused stumbling, misfires, etc. Bought new pins from the dealer and rebuilt the connector and have not had a problem since.

Here?

[gtdragon980]

Yes that is it, unscrew it from the fuel injector harness and take a look at the sockets/pins in there and see if there's greenish corrosion in there. It can cause a lot of the problems that you have.

[phenryiv1]

Yes that is it, unscrew it from the fuel injector harness and take a look at the sockets/pins in there and see if there's greenish corrosion in there. It can cause a lot of the problems that you have.

Thanks!

[jlevie]

I THINK it was pin 20, and yes, it smoked (in the ground point behind/above/left of the steering wheel (thank God the dash was out!!!). I was hoping that it only killed the DME so I swapped DMEs to no avail.

There is little chance that the harness escaped damage. But you might be able to fix it. Remove the harness from the car, cut it open and inspect/repair.

Harness was a '90 harness so I assume it was late model. Might I try to source an '87 harness to simplify things? Will an '87 "i" harness work with a '90 "i" motor? Would my '87 eta harness (still a Motronic...) work on the "i" motor?

An 87 M20B25 harness would be plug-n-play, but might be hard to find. A later harness will work with a slight mod for the tachometer/econometer. An ETA harness won't.

[K1CKBAC]

The exact thing happened on my car on pin 20. May not seem like it but in my case the harness got burned throughout.

[shiboujin]

Hey guys! Look what I found!

http://www.sears.com/shc/s/p_10153_12605_03482141000P?sid=IDx01192011x000001&kispla=03482141000P&srccode=cii_17588969&cpncode=30-137678232-2

[irish44j]

Yoshi - we discussed that this afternoon....test each pin vs. the wire output. We may work on that on his car tomorrow at the rally-x when we get tired of driving. I'm bringing my multimeter (actually, the same one you linked, lol).

[shiboujin]

w00t! Diagnostics! text me when you guys are checking it. If I'm free, I'll walk over.

[irish44j]

well, Pat will be in the paddock all day until the car runs, so come over whenever. The rest of us will be running on and off depending on how the day goes. We'll have a wiring party, lol.

Looks like Spencer may have a full harness he can bring as well...

You know where the rally-x paddock is? gravel access road go straight past the bridge (across from the main circuit pits, basically).

[phenryiv1]

Update:

Awapped in 4 different working AFMs. None resulted in any change. I ASSUME that my AFM is working properly.

The C191 harness was a little corrodded. I was at the track and did not have much with me in terms of cleaning supplies, so I wrapped the handle of a screwdriver in paper towels and did my best to clean off the side of the C191 that had the "female" ends of the pins.

Fail. From that moment on, the car has refused to start.

On a relatred note, others there helping with diagnostics also thought that I had lost spark at that point, as any plug wire pulled form the spark plug had no "tick-tick-tick" as it would if the wire was trying to fire. Obviously I had spark before, as the car was running.

As we were doing diagnostics, someone noted that my CPS lead was not properly secured to the timing cover and that the wire at the seonsor end was flopping all over the place. We inspected it and noticed that one lead was (now) completely broken and the other was a thread. I got excited, thinking that this could explain the bad idle AND potentially the lack of spark.

Our working theory was that the CPS was the issue, so it was recommended that I replace the CPS. With no CPS handy, we were dead in the water at that point.

The plan: 1) Replace the CPS, and 2) clean and re-connect the C191.

I took it home and Sunday I replaced the CPS with a working unit from another M20 (this one looked pristine).

Next, I used proper electrionics contact cleaner and a soft cloth and tried to start the car. Nothing.

I applied dielectric grease individually to the male pins in the C191. Nothing.

Still in a bad spot, AND I have gone backwards from running (but poorly) to not starting at all.

Thoughts?

[gtdragon980]

So you are sure there is spark present as of now? FP is good? The wire harness was fried correct? If so, you have not replaced it with another known working one? I would do this stuff first, but then again, I'm sure if you're good with electronics you can test your harness to make sure it is working correctly before replacing. I'm sucky with that so I just end up replacing it.