High revving Engine!

pep59 · Post by **pep59** » Tue Oct 26, 2010 11:15 pm

Hello again,
I just rebuilt my injectors last week.
Tonight as I was driving down the street, my engine starting revving uncontrollably high. I had to pull over and shut off the engine (luckily only a few blocks from home). When I restarted my car, the engine immediately revved high. It was too dark for me to really see anything so I will have to go back tomorrow in the daylight so see what I can see.

Any ideas or troubleshooting help would be greatly appreciated!

Thank you very much....frustrated 79 528i owner

GripGreg · Post by **GripGreg** » Wed Oct 27, 2010 1:21 am

Wow! Sorry.
You re-built them; or you HAD them re-built? Two differant things, ya know?
Did this happen before the re-build?
I can't help, but, I can ask questions for the big dawgs!
Good Luck,,,,Greg

DMS · Post by **DMS** » Wed Oct 27, 2010 6:56 am

Sounds like an awsome air leak somewhere.

Did you take any hoses off? Is you throttle linkage stuck somewhere?

pep59 · Post by **pep59** » Wed Oct 27, 2010 8:42 am

Sorry, to be more specific, I pulled the injector rail because one of the connecting hoses from the rail to the injector was leaking. The injectors were flow tested and came out fine. I replaced all the connecting hoses from the rail to the injectors, the big rubber rings around the base of injectors, one snap ring, and the small o-rings where the injectors fit into the intake manifold.

I had a pile of hoses disconnected (among other things) while doing the repair. The engine seemed to run fine for awhile after the work I did so I am not sure if this symptom is related or is something new.

Is there a logical sequence of things to check when working through this problem?

Thanks again...pep

pep59 · Post by **pep59** » Thu Oct 28, 2010 4:41 pm

So my sons and I pushed the car home last night! Just over a mile with the last 1/4 a nice uphill gradient.

Today, I could not see anything obviously wrong under the hood.
The throttle linkage was not sticking but I sprayed some penetrating oil inside the cable sheathing and on spring/coils on the intake.

When the car starts, the RPM go to 4000 so I shut it off pretty fast.
It may or may not be relevant but it is near/below freezing when I live.

Any and all ideas would be greatly appreciated!...Thanks.

79 528i

Blaise · Post by **Blaise** » Thu Oct 28, 2010 5:26 pm

I would take the air filter off and inspect the AFM and the throttle body.

See if the AFM door is free and closing when idle.

Then see what the throttle body butterfly is doing. From what you state, I understand that it is closing as it should. But for the motor to rev like that, I imagine that it is getting good air and fuel. Even if you injectors were dumping fuel, it should be overly rich without an proper dose of air.

Could you have plugged something in too loose and it came undone when you where driving....sending the computer the wrong message?

Just some thoughts.

Spend sometime rechecking where you have been. Relax and be thorough.

pep59 · Post by **pep59** » Thu Oct 28, 2010 6:59 pm

Blaise,

Thanks for the advice, it turned out to be golden!

When I was disassembling the air hoses on the intake, I found that the hose clamp on the accordian hose closest to the intake was positioned such that the screw head actually had jammed the linkage partly open. I had assumed the linkage was moving freely but failed to notice this until I had taken everything apart again.

Happy motoring once more!!!

Blaise · Post by **Blaise** » Thu Oct 28, 2010 10:09 pm

Good to hear.

Now that you mention it, that happened to me once. I reassembled everything and took my girlfriend for a ride. The car could barely make it over 30mph. I opened the hood to find that the same hose clamp was keeping the throttle linkage from moving much beyond idle. Nice to have a tool kit onboard.

Glad you found it.

alotawatts · Post by **alotawatts** » Fri Oct 29, 2010 12:11 am

I too have experienced this intake-throttle 'engineering feature'. If you think about it...it's dangerous !

GripGreg · Post by **GripGreg** » Fri Oct 29, 2010 12:19 am

Everyone; pay att'n to how you put things back together! If you're not around to push me in the right direction when I peek out from my small shade tree, I'll be lost!! Thanx for everything you continue to help with.

DMS · Post by **DMS** » Fri Oct 29, 2010 2:32 am

Glad you found it.

pep59 · Post by **pep59** » Fri Oct 29, 2010 6:43 pm

Thanks DMS et al,

You actually called it first!

Thanks again to everyone for their comments and ideas!

T.Hanson · Post by **T.Hanson** » Fri Oct 29, 2010 11:13 pm

I set the big hose clamps to look cool and be accessible. Start up was fine, but when (sitting) I hit the pedal to see if it would stumble, it stuck wide open.

Experience shut the key off as soon as the pedal stayed down, no big RPMs.

Sure enough, it it very possible to position the hose clamp to allow the linkage to rotate and click, stick under the screw deal.

RonDwyer · Post by **RonDwyer** » Mon Nov 01, 2010 11:56 pm

The fun of older cars is figuring out how to fix it before you open the hood. I decided to sell the TDi and get another older car.

DMS · Post by **DMS** » Tue Nov 02, 2010 10:11 am

RonDwyer wrote:The fun of older cars is figuring out how to fix it before you open the hood. I decided to sell the TDi and get another older car.

You can apply that to the TDi aswell but the system is more complicated so you have more parameters which you can turn.