1992 E34 M5 Restoration Project

[Alex/M5]

Hey guys, first post here so here goes. Have a 1992 e34 M5 (s38b36) ,car was a barn find but in generally good shape, however she has some strange issues.

Issue #1: Car hunts for its idling point when warm (revs gently between ~600 rpm and 1000 rpm without any throttle input) . Doesn't do it when cold.

Issue #2: Car starts to hesitate/bog at around 6000 rpm for a few seconds and then pulls through to the redline. However, it only does this when you pin the throttle. If you roll onto the gas slowly it doesn't hesitate. Also have intermittent popping under compression. Replaced fuel filter and no luck, so maybe bad injectors or fuel pump?

I have checked that the resonance flap doesn't self test at start up so that could be adding to the problems. However, the actuator doesn't seem to be the issue since I connected a line to it ,sucked on it and it worked (so I'm thinking bad solenoid or vacuum leak?) all the hoses seem fresh though.

The car is going into the shop early in the new year, so will get them to check all the vitals (fuel, air, spark and compression test). Overall I'm left feeling a bit despondent with the performance. I realize its an old+heavy car and not that torquey but honestly thought it would feel a bit more alive, my dad's 1969 E-type feels way stronger haha. Does anybody know a reputable mechanic/garage in the Western Cape that works on these older m cars? Any advice would be greatly appreciated. Will report back with info as I go along.

Thanks in advance

 

[Kyle]

Hi bud,

Considering the car was a barn find, that would mean it would have been parked for a while. Before trying to perform any performance tests or hard driving, you should do a complete fluid change. Then the basics like plugs, filters etc... The fuel system would have been sitting with old fuel in it, so the tank would likely need to be cleaned properly, fuel lines inspected and injectors serviced.

Warm idle hunt usually points to a vacuum leak, which any reputable mechanic should be able to test for...

 

[Alex/M5]

Hi bud,

Considering the car was a barn find, that would mean it would have been parked for a while. Before trying to perform any performance tests or hard driving, you should do a complete fluid change. Then the basics like plugs, filters etc... The fuel system would have been sitting with old fuel in it, so the tank would likely need to be cleaned properly, fuel lines inspected and injectors serviced.

Warm idle hunt usually points to a vacuum leak, which any reputable mechanic should be able to test for...

Really appreciate the reply, the fuel tank was removed and thoroughly cleaned (forgot to mention that) Good point on the fuel lines though, will definitely have that checked.

 

[gavsadler]

Calling @Benji

 

[Peter@AEW]

Remove the plenum so that you may get to the idle control valve and at the same time to the smaller vacuum hoses which need to be checked for cracks and perished ends.
When an engine is steady whilst cold and starts hunting when hot more often than not it is sucking un metered air which will show up as erratic idle when hot.
Clean the ICV with petrol by dipping it or carb cleaner,
Make sure the throttles are all at the same gap when closed or open.
Change spark plugs air filter fuel filter
Set valve clearances
Also do a fuel pressure test.
Remove fuel injectors and clean them in thinners by soaking them for a few hours whilst changing the thinners regularly.

That specific engine is low on torque in the mid range (relatively speaking) so do not expect any great performance.

 

[Alex/M5]

 

[Benji]

Please share more pictures! Rare to find in that colour

So as per previous posts, I would start by removing inlet manifold and replacing all the vacuum pipes and cleaning ICV with carb cleaner. Change the o-rings between the inlet manifold and throttles. I bought new ones from BMW (was about R200 for the set) but they still leaked. I then got one size thicker (cant remember the exact details now) o-rings from an o-ring place and that solved that leak. Easy to check for vacuum leaks with a positive pressure air pump (vacuum cleaner in reverse lol) and soapy water. Change spark plugs and check/clean/replace the distributor cap and rotor.

Also what is the part number of your TPS? These can fail and people replace them with M30 ones (they look identical but work different) which will cause all manner of issues. Do you hear the TPS "click" just before closed throttle? Could be that the TPS is not in the "idle" position which can cause hunting.

 

[Benji]

Having said all that, the E34 M5 is not that fast, especially at altitude A Golf GTi will drive away from you, but you'll have a bigger smile on your face

 

[Alex/M5]

Having said all that, the E34 M5 is not that fast, especially at altitude A Golf GTi will drive away from you, but you'll have a bigger smile on your face

Hi Benji really appreciate the reply! Thanks for the compliment, the lazure blue looks great... changes to purple depending on the light.

The TPS doesn't make any noise (at least from what I can hear) . From what I can make out the part # is Bosch 0 280 120 404. When everything opens after new year will go through everything with the mechanic. Vacuum, spark, fuel , valves sensors etc. Will keep this thread alive with updates along the way.
Here's some pics for the mean time

 

[Solo Man]

I remember from having various 535i's in the eighties and nineties that they do not like it when the dipstick and oil filler cap or even the petrol cap is not air tight as the leaks there causes the car to hunt at idle and affects the performance as well. On one of my E28? 535i the pipe on the tappet cover leading to the inlet manifold iirc was perished and that also caused a lumpy idle. I taped that up and the idle was back to normal. Just my 2c's

 

[Benji]

Hi Benji really appreciate the reply! Thanks for the compliment, the lazure blue looks great... changes to purple depending on the light.

The TPS doesn't make any noise (at least from what I can hear) . From what I can make out the part # is Bosch 0 280 120 404. When everything opens after new year will go through everything with the mechanic. Vacuum, spark, fuel , valves sensors etc. Will keep this thread alive with updates along the way.
Here's some pics for the mean time

Car looks so clean That TPS seems to have the correct part number. There is a very audible click when the TPS reaches the "idle" position (car off). Undo those 2 screws and adjust the TPS so it just clicks when the throttles close. There is a microswitch that clicks inside the unit.

This TPS has 3 "work modes": Idle (throttle closed), partial load (from small opening to about 70% open) and full load (over 70%)

 

[Kyle]

Hi Benji really appreciate the reply! Thanks for the compliment, the lazure blue looks great... changes to purple depending on the light.

The TPS doesn't make any noise (at least from what I can hear) . From what I can make out the part # is Bosch 0 280 120 404. When everything opens after new year will go through everything with the mechanic. Vacuum, spark, fuel , valves sensors etc. Will keep this thread alive with updates along the way.
Here's some pics for the mean time

What a beaut!

 

[Alex/M5]

Alright so some news! Car went to a decent mechanic and he found massive vacuum leaks (pipes were old and one wasn't even connected). He also wasn't happy with the coil and 2 of the HT leads and also found the gaps on the sparkplugs were incorrect. Injectors were sent away, cleaned, spray patterns optimized, and new O rings. Car goes like a bat out of hell now! Don't even recognize it anymore. I take back about what I said about this car being slow, it isn't. Ok it is if you compare it to an m240i, but objectively speaking the 3.6 E34 m5 is still quick. Not much under 4k rpm but as you get over that and towards the redline it pulls strong. Thank you to everybody for your suggestions and help. Many of you were right. If I get a chance I will post some vids of the car.

 

[shauwn]

Alright so some news! Car went to a decent mechanic and he found massive vacuum leaks (pipes were old and one wasn't even connected). He also wasn't happy with the coil and 2 of the HT leads and also found the gaps on the sparkplugs were incorrect. Injectors were sent away, cleaned, spray patterns optimized, and new O rings. Car goes like a bat out of hell now! Don't even recognize it anymore. I take back about what I said about this car being slow, it isn't. Ok it is if you compare it to an m240i, but objectively speaking the 3.6 E34 m5 is still quick. Not much under 4k rpm but as you get over that and towards the redline it pulls strong. Thank you to everybody for your suggestions and help. Many of you were right. If I get a chance I will post some vids of the car.

how much was the cost for the injector service and who did you send it to buddy?

 

[Benji]

Alright so some news! Car went to a decent mechanic and he found massive vacuum leaks (pipes were old and one wasn't even connected). He also wasn't happy with the coil and 2 of the HT leads and also found the gaps on the sparkplugs were incorrect. Injectors were sent away, cleaned, spray patterns optimized, and new O rings. Car goes like a bat out of hell now! Don't even recognize it anymore. I take back about what I said about this car being slow, it isn't. Ok it is if you compare it to an m240i, but objectively speaking the 3.6 E34 m5 is still quick. Not much under 4k rpm but as you get over that and towards the redline it pulls strong. Thank you to everybody for your suggestions and help. Many of you were right. If I get a chance I will post some vids of the car.

Awesome! Enjoy your special car

 

[zabbo]

Great news!! Now where are those vids?

 

[Alex/M5]

how much was the cost for the injector service and who did you send it to buddy?

Was about R1200 with J&S auto tech Somerset West

 

[Michele Mathison]

Alright so some news! Car went to a decent mechanic and he found massive vacuum leaks (pipes were old and one wasn't even connected). He also wasn't happy with the coil and 2 of the HT leads and also found the gaps on the sparkplugs were incorrect. Injectors were sent away, cleaned, spray patterns optimized, and new O rings. Car goes like a bat out of hell now! Don't even recognize it anymore. I take back about what I said about this car being slow, it isn't. Ok it is if you compare it to an m240i, but objectively speaking the 3.6 E34 m5 is still quick. Not much under 4k rpm but as you get over that and towards the redline it pulls strong. Thank you to everybody for your suggestions and help. Many of you were right. If I get a chance I will post some vids of the car.

Hi Alex, who is this rare bread of decent mechanic you talk of? Great to hear your m is running so well!

 

[Alex/M5]

Hi Alex, who is this rare bread of decent mechanic you talk of? Great to hear your m is running so well!

Hi there, Helderberg auto tech is not bad, also J&S auto tech Somerset West. Both are Bmw master-techs to the best of my knowledge.

 

[Alex/M5]

Hey Gents, happy new year to all of you.

Brief update: the M5 is doing well a year on from buying it. Plenty of progress has been made.

1)Turns out the resonator flap was not working (even though we thought it worked we never checked to make sure, lessoned learned), we pulled off the plenum to find the incorrect diameter vacuum lines and the one-way valve was installed... the wrong way. Rectifying these things fixed that issue.

2) ABS light came on. Cleaned all the sensors and also found one of the wires from the rear right sensor had been broken (the one near the battery) fixed that and light went out.

3) Sent warning computer box away to be refurbished. False warning codes gone.

Now, onto the next thing + my question. To preserve this wonderful engine I aim to adjust the valve clearances as I feel this needs to be done. I'm aware that one needs some tools like the special bucket depressing tool, valve cover gasket, and obviously new shims. I was wondering if anybody knows where I could order s38b36 shims in SA, as well as the special tool to depress the bucket to remove the old shims? Any info on this would be appreciated.

Cheers