Engine Trouble After Minor Engine Work

#1

I am new to SE30 and having engine problems I can’t figure out. I have never posted here, but have spent a lot of hours reading since I bought the car, and this is by far the best forum I have ever seen. Incredible amounts of information here. I figured I would try my luck and see if I can borrow some knowledge.

The car ran great when I bought it, and after what I thought was some minor work, it will barely run.

What I have done since it last ran well:

  • Timing belt/water pump
  • removed AC and PS
  • Throughly scrubbed and hosed off engine bay with purple power degreaser
  • Stripped interior and removed dash for cage
  • After I already knew the engine wasn’t running well, replaced plugs, air filter, and adjusted valves. No change.
  • After I drained coolant and removed radiator for timing belt, I got very busy and the car sat drained for about a month before I got back to it.

Car starts fine, but idles very rough and boggs immediately when you try to give any gas. Acts very, very much like the timing is off. Since I just did the belt, I did the obvious thing and pulled the upper cover off to check the marks and they are right on. I have since checked 5 times hoping for it to be off, since that’s the easy and obvious answer, but (go figure) no change.

The exhaust reaks of fuel when running, so if the timing is OK, it seems like I have an A/F mixture issue.

Thoughts/Questions:

  • Does anyone know of the obvious car prep mistake? Is there something that I threw away that I shouldn’t have, or something below the dash or out near AC or PS that I would have unplugged or damaged? Something I unplugged to remove something else and just forgot to put it back? Haven’t found any of these things, but would love to.
  • I have since plugged the dash back in to do the stomp test to try to read codes, but it doesn’t work (have 173 Motronic). I was thinking maybe bad TPS would cause that, but I did the Bentley checks, and it seems to be fine. Anyone have any idea what causes this? I feel like this is a good clue as to what the real problem is, although I don’t know yet what it means.
  • Could I have damaged coolant temp sensor or any other sensor while the coolant was drained for so long?
  • Purple power eats the hands pretty quick without gloves, anyone ever heard of this damaging wiring/sensors? Some other known issue with hosing off the engine? By the way not a clean engine freak, had leaky valve cover and oil pan gasket which put 1/4" of sludge on everything.
  • I have tried not to go too crazy digging into things on this since it ran great before I touched it. I assume the problem is something I just did, although I am quickly running out of the easy stuff.

Any help would be great.

Thanks,
Chris

#2

I would guess you tore a nice hole in the intake boot when you did the timing belt.

#3

The first thing to suspect is a vacuum leak. Get a can of starter spray and start the car. Spray it around the engine bay and see if the engine surges. That’s your vac leak.

Alternately have a shop do a smoke test or do a DIY and make one.

#4

Swap the fuel pressure regulator and crank position sensor with some known good ones. Make sure your throttle position sensor, idle air control and air flow meter are plugged back in.

#5

turbo329is wrote:

If you’re suspicious of fuel, get a fuel pressure gauge from Harbor Freight. They are dirt cheap.

#6

Consider replacing your fuel filter. Simple to do, good preventive maintenance regardless and a clogged filter can produce all that your describe.

#7

Spare time is rare lately, but finally got a chance to order parts and try everyone’s suggestions this weekend. Still no change.

  • No major tear in intake boot, although was in bad shape and did have several ~1/2" long cracks that could have gone all the way through. Replaced.
  • Crank angle sensor, and fuel filter replaced.
  • Fuel pressure within spec.
  • Vacuum leaks - I used to have a 1967 VW Karmann Ghia with aftermarket engine which for some reason dissolved/melted/ate the gasket at the carbs. Very short intake section and Ether spray test worked like a charm to diagnose. Tried this at first with the E30 and got no revs. Pulled the intake boot just slightly off the AFM to create vacuum leak and sprayed in. It takes a long spray directly into the opening to get much of a rev at all. Definitely does not react to a passing spray around vacuum hoses and connections. Am I missing something? Anyway, no vacuum leaks yet, and rechecked hoses and connections visually. All look OK.
  • Replaced distributor cap and rotor while I was buying things.
  • Put timing light on each plug wire to check that all have spark. Seems like good consistent spark at all cylinders (new plugs last time I worked on it).

Couple Questions Again:

  • Forgot to mention in my first post that the crank pulley/vibration damper was completely seized when I tried to remove it for timing belt. Finally got it off with pulley puller, but bent it, so had to buy a new one (ebay). As I ruined the old one I found out that the outer teeth for the position sensor are actually on a separate thin ring that is pressed onto the damper. Is there any way that ring could somehow be rotated out of position on the used one I just got? I don’t see any alignment marks between the damper and the ring.
  • Anyone know ignition timing spec. Since it’s not adjustable, I can’t find a spec anywhere, but it would be nice as a second verification the timing ring and timing belt are right.
  • No check engine light through any of this. My new car stutters once and the damn thing stays on for a month. Does it point to something that the light isn’t on? It lights at startup, so I know its not just bulb.

Thanks for the help

#8

Make sure your actual engine cam to crank timing is correct without the use of the timing marks. Check actual piston #1 TDC in relation to camshaft. Marks may be off due to your damper being installed incorrectly.

If off, check compression and leak-down for possible valve damage, after correcting timing.

Also check actual engine vacuum with vacuum gauge. Should be around 17 to 20 hg steady reading. Vacuum gauge is one of the most overlooked tools for engine troubleshooting.

Peter Thibault

#9

Thanks, I will try those.

Also made me realize why my Ether test by AFM didn’t work. Since AFM is obviously upstream of throttle valve it’s not vacuum, and really hardly negative pressure at all during idle. Also sprayed all around throttle body over the weekend and still got no revs. Will keep trying.

#10

It sounds to me like you have intake leaks. The only sure way of locating them is to have a smoke test run on the intake. Other causes are possible, but until intake leaks can be ruled out there is little point in investigation the other possibilities.

#11

Chuston22 wrote:

[quote]Thanks, I will try those.

Also made me realize why my Ether test by AFM didn’t work. Since AFM is obviously upstream of throttle valve it’s not vacuum, and really hardly negative pressure at all during idle. Also sprayed all around throttle body over the weekend and still got no revs. Will keep trying.[/quote]

There’s plenty of places for vac leaks that are not near the throttle body. Hose to brake booster. Hose to fuel vapor recovery cannister. Hose to fuel pressure reg. Hose to rocker arm cover.

PThibault: I’ve not done a vacuum test before. Where/how, in the intake track, do you connect it?

#12

Ranger wrote:

True! The complete list of possible causes of an intake leak is:

Intake boot
Throttle body gasket
ICV hoses & connections
Brake booster, hoses, and connections
Crank case breather hose
Evaporative control hoses, valve, and expansion tank
Fuel pressure regulator & hose
Injector seals
Valve cover gaskets & bungs
Oil filler cap
Dip stick o-rings
Oil return tube o-rings

#13

Getting very close. Ripped everything apart looking for leaks. Found some by the Idle Control Valve and fixed. No major change in running, but the check engine light finally came on. Stomp test still didn’t work.

Happened to be browsing the classifieds on here, and found a DME for sale for $40 - Not a bad spare to have whether I need it now or not. Plugged it in, no change in running, but stomp test works. Got code 1252 which is fuel injector Group 2 fault, so starting digging around the injectors.

-first noticed that when I unplug injectors 1,3,5 while running it makes the engine run terrible (as expected). Unplug 2,4,6 and no change. On other cars it wouldn’t surprise me if some only kick in at high flow, but since E30 has individual injector for each cylinder, all have to be running and the engine should stumble when one stops.
-Did Bentley tests on injectors and plugs. Injector resistance fine, 12V from red wire to ground fine. Also get 12V from other wire which seems weird.

  • Did Bentley tests at DME connector. Jumper terminals 2 and 36, touch terminal 17 to ground, and half of the injectors click as they should. Same thing and touch 16 to ground and nothing happens (should have been other half of injectors). Pulled connector apart and faulty terminal 16 is brown and white wire.
  • Traced thru engine compartment and made it to the twist connector under the throttle body. Connects from DME to injector harness that runs up thru intake manifold. Pull off bottom boot and connector is full of water which wasn’t helping. Finally get connector untwisted, and brown and white wire is pulled from connector. I could have broken the harness and filled the boot with water when I cleaned the engine.
  • Doesn’t seem like I can fix the connector so will have to splice in replacement.

Found a couple of $200 harnesses on ebay, but anyone know where to look for cheap used parts - harnesses or other. Junk yards here are worthless. Usually about 75% cost of new and never have anything. Anyone have this connector, or a spare engine harness they would like to sell?

Trying not to get my hopes up, but feel good about this one.

#14

I might have one available. Can you take a picture of the connector you’re looking to replace?

#15

The connector is the round one under the manifold for the injectors. I dimly recall it as C101. Have to cut a hole in it so it will drain, otherwise it corrodes. Some carefully applied conductive paste is a good idea too.

You just want the injector connector, or do you want to buy a whole engine harness? Or is it the injector harness that you want.

Have to be careful about swapping whole engine harnesses. Some folks say that late model and early model are different. I can’t gainsay that myself.

If it’s just the connector on the engine harness that you want, $20 and I’ll cut one off of a spare harness and send it to you. Paypal Scott(at)Gress(dot)org

You could just go to Radio Shack and get a Molex connector. Then make your own C101.

#16

Couldn’t wait to see if the new find would fix the problem, so went out today and just crimped in a new section of wire around the connector for the one wire that was broken. After everything was back together, it fired right up and runs great.

I intended for my little jumper to be temporary, but don’t feel like cutting things back out that work, so don’t think I will need a connector anymore. Thanks for everyone’s help on this.

#17

Good news!! I was at the shop earlier this morning and I def. have an extra plug. If you change your mind it’s yours.

#18

I was going to say be careful of washing these engines off as water can get into the connectors and boots and cause major headaches. Congrats to Ranger for recognizing the injector connector under the intake. This is a major culprit.

In another instance I had a freind whom washed his 318is engine. It started running like crap and would not accelerate past 4K rpms. After replacing the fuel pump, injectors, crank and cam position sensors, he finally was going after the AFM. When he unplugged it, water dripped out of it. The signal wire was completely green and corroded. Cut it off and spliced on a another connector, viola, engine ran like a champ.

Expensive lesson learned.