3 Typical 1 Very Odd DOHC Problem

[radman3120]

Well, I'll start with the odd one first because thats the one I really need help with. I have a '93 Z34 with the 5 speed and for some reason the first couple times I start it up in a day (I do a lot of short driving) it spews coolant from the coolant temp / intake gasket region towards the rear of the engine bay (both the sensor and gasket are relatively new). It doesnt look like it's the intake gasket which I had to replace twice this year. I pressurized the system a week or two ago (when all I knew was that I was losing antifreeze) and thought it looked like it was dripping from the threads of the coolant temp sensor so I took it off, cleaned off the teflon tape, and applied liquid thread sealant and tightened it a little further. Now it spews it but I dont know where from because its really hard to see under there. The crazy part is that after it stops spewing coolant after a couple minutes it doesnt seem to leak any more coolant. Last weekend I drove four hours to Pittsburgh and did not lose any coolant. Has anyone had experience with this at all?

 

 

Now for the typical problems you should all know a bit about:

(1) Long Start - it always starts on the second try

(2) Random Idle Speed Increase - When idling it will randomly rev the engine to about 2000 rpm.

(3) WOT miss / putter / something - usually at higher rpms as if the ignition system is cutting out or the fuel pump cant keep up

 

I tried the A/C sensor disconnect and idle relearn which seemed to work for a short time to correct the idle increase and hard start but then it went back. The other two 5 volt sensors that supposedly can also short out ignition on start, the MAP and TPS, seem to read fine. The WOT miss does not happen all the time but when it does it only happens at high rpms. I also switched the fuel pump relay out with a working relay. I think I am going to put in a fuel pump as it is the only thing I can come up with for the hard start (no prime, Im not sure I hear the pump when I start the car, and the car has to wait for oil pressure build up?) and WOT problem (Only does it at high rpms so maybe fuel isnt being pumped in fast enough and I have relatively new plugs (but I heard bosch are bad to have) new 8 mm wires and that leaves only the coils). Is there anything else I can check out?

 

Sorry for the long post but I need some help! - Thanks

[DaveFromColorado]

with the coolant problem - you may have done what I did once on an old car...

 

ran it in too deep and cracked the aluminum part it screws into - this can happen without even noticing it - I'd look into that.

 

as to the other three problems - it's too early for me to even thing about 'em.

 

--Dave.

[z34_nut]

well those "usual" problems I have never delt with in my life on either of my z34's...

[fastbird232]

If I have my car in park and rev it to 4k, it coughs and cuts out too. I remedied the problem by not revving it to 4k in park any more. Mine also takes time to start sometimes. I'm interested to hear any ideas someone else might have as well.

[GP1138]

If I have my car in park and rev it to 4k, it coughs and cuts out too.

 

That's called a rev limiter. It's not a problem.

[fastbird232]

Oh. I thought it didn't kick in 'til redline. Stupid me.

[skiiirt]

Now for the typical problems you should all know a bit about:

(1) Long Start - it always starts on the second try

 

Try replacing the fuel pressure regulator

solved that problem for me

[radman3120]

Within the next couple days i will be taking the car to my dads friends garage to check the fuel pressure and whatever else i can look at to test the fuel pump and fuel pressure regulator....

 

Also, as for the coolant leak I did some more pondering and looking around and it does look like there is a potential of a simple bypass hose but every time i try to look it is too difficult to see and the leak stops by the time i get anything taken apart. One of these mornings im going to take the air box off before i start it and look around that way.

 

I'll let you know what i come up with

 

By the way, i've also been told that my idle problems could possibly be cause of the EGR valve. Is my car showing the typical symptoms of a clogged or bad EGR or at least what are those symptoms - Thanks

[/u]

[GnatGoSplat]

Now for the typical problems you should all know a bit about:

(1) Long Start - it always starts on the second try

(2) Random Idle Speed Increase - When idling it will randomly rev the engine to about 2000 rpm.

(3) WOT miss / putter / something - usually at higher rpms as if the ignition system is cutting out or the fuel pump cant keep up

 

These problems sound to me like a lower intake manifold gasket, but you already replaced it twice you say? The lower, not the upper?

 

Not sure on the coolant leak. If I were to just take a random guess, I'd say it might be the head gasket.

[Hairdo12]

(3) WOT miss / putter / something - usually at higher rpms as if the ignition system is cutting out or the fuel pump cant keep up

 

Dont forget about that ignition control module. I have the 3.1 but the ICMs are the same... mine did that for about 2 years and then one day #1 and #4 are dead.

[sonyman87]

the car runs so the modules are NOT dead.

 

When a motor revs higher the compression raises in the combustion chamber making it harder for the electricity to jump across your plugs. More gas and air.. so i put money on fouled plugs and warn plug wires. your ignition system else wise should be fine. + when you are running in a fouled state it james up the 02 sensor with carbon sometimes giving crapy readings and might as well crap out your egr. i would recomend replacing the 02 senosr and taking the egr off to clean it.

 

i hope this helps you a ton!

[digitaloutsider]

My 3800 stumbled all over itself when a coilpack went bad. IThat could very well be the problem.

[radman3120]

Well, i took off the air box and found sorta where the leak is coming from. I have some pics here: http://www.cardomain.com/ride/553386/12.

 

Also, new AC plugs are definitely going have to to go in soon instead of the crap bosch that are in there now. O2 sensor and plug wires are new but ill have to take off the egr and clean it. Coils are origninal so there is a possibility of weakening coils.

 

Ill have to see what I come up with and I will let you all know. Im at college now so it might be a little longer but I or my dad will definitely be working on the car.

 

Thanks again.

[radman3120]

Just wanted to let everybody know that I havent given up on this thread I just havent been able to make it home at all to work on it. Next week I should be able to get something done and I'll be back with at least some sort of diagnosis. Thanks