sogabe

a 91 v6 RS auto trans.

Ive been having problems after problems.
I did a lifter job and valve adjustment,(new thermostat and gaskets)
since then Ive been having weird problem and even mechanics cant figure whats wrong.

here's my symptom:
my car runs and idles fine at cold temp.
once my car warms up, it starts idling rough as its almost gonna stall(but it doesnt)
also my temp gauge has been reading lower than where it should be,
it never pass 160F.

could my new 180F thermostat cause this?
or could I have overtighten my valve or something?

my car do run fine when warm, just idles rough,
I think my ECM is reading lower temp than it should be and it runs too rich or something but I dont know how to fix it.

just within last week I paid almost 800$ total for all these other repairs
and Im about to reach my max credit card, I work 7bux an hour and I cant afford anymore repairs and my parents want me to sell the car but I dont want to.. so if any1 know anything I appreciate it in advance!!!

86camaro383

iTrader: (3)

so wait, let me get this straight, your freaking out cause your temp gauge isnt wear you want it to be?

Okay, check it out.... You replaced the thermostat with a 180. Stock probally calles for a 195. Your thermostat is either the wrong one, or its defective. New doesnt mean its good. Its running rough because the ECM sees its running cold, and is dumping more fuel into it.

SSC

I'd suspect it may be a timing issue. It sounds like the car is going into closed loop since it runs bad when it gets to operating temp so the t-stat apears to work well enough in that reguard. You may double check your valve lash too since it cant hurt to have that set correctly.

sogabe

my upper radiator hose is hot, so I know the thermostat is opening, i havent checked if its stuck open though.


I might double check my timing, and my valve lash then.

Im just freaking out caz if this symtom were known to lead to another problem, Im already in debt and I will have no car plus Ill be forced to sell the car..

but I guess it isnt as big of a problem as I thought,
thanks for the tip guys I appreciate it

V8Rumble

iTrader: (2)

Just a couple of thoughts, off the top of my head -

First off, if you suspect the thermostat, yank it out. It's real easy to do, & if you know someone w/ a candy thermometer (or one of those cool remote IR ones), it's easy to see what temp it's opening up at.

Second, (I think that) it's also possible that the valve lash is set incorrectly. If it's too tight, then it might work OK when the engine's cool, but as it warms up & everything expands a bit, things could tighten up to the point where there's more friction on the valvetrain. The ECM could be adding fuel in order to keep the engine running, but if there is this additional friction, it could wipe out a cam lobe or some other part of the valvetrain in fairly short order.

Now let me emphasize again that this is just speculation/off the top of my head - I haven't put a whole lot of thought into it, it's just the first two things that jumped into my head. It's probably something minor, and there are others here who can probably give you a better idea of what's likely happening. But checking the thermostat is pretty easy & cheap, and checking the valve lash isn't too much worse. If nothing else, you can eliminate two of the possibilities.

Good luck!

(Just saw that SSC addressed the valve lash idea...)

sogabe

thanks v8rumble.

I knew the heat expands the valve, and thus it doesnt seat as tight as when cold and gives a little gap, and gives me low compression or a misfire?

but I think ur thought makes sense to me how ECM is trying to send more fuel so the car doesnt die. I will open my valve cover and loosen up a bit to see what happens, thanks so much!!

Supervisor42

Here's another take on it. With hydraulic lifters there would have to be one valve so tight that the lifter would have to bottom. That's the whole idea behind hydraulic lifters: they allow the valve train some room for misadjustment. Also the thermostat being stuck open/too cold should make it just get poor mileage, it should run like an engine that isn't warmed up yet if the ECM is reading the coolant correctly. I would suggest checking the ECT (engine coolant temp) sensor and the O2 sensor. These will make it run bad when it enters closed loop. If the engine is worn out it will lose compression when it warms up and have trouble idling when warm. Do a blow-by check before buying the O2 sensor. With the engine warm, idling in drive, brakes on, wheels chocked, take the oil filler cap off and increase the rpm to 1500. If you have a bunch of smoke coming out (6" tall plume), put a for sale sign on it that says: "needs tune-up". If it passes buy an O2 sensor.

naf

iTrader: (7)

Go back and look at the things you did before it started running rough.

"I did a lifter job and valve adjustment,(new thermostat and gaskets)
since then Ive been having weird problem and even mechanics cant figure whats wrong."

Think gasket leak or valve adjustment issues. It's unlikely that other things that were working fine before you did this work are failing now. Put the old t-stat back in if you want to rule this out.

When it's idling cold it should be idling at a slightly higher rpm (and running richer), is this contributing to the smoother idle while cold?

Why did you replace the lifters?

sogabe

thanks guys for more info.

I do tune up very frequently,
my o2 sensor is one of them so they're about a month old.

I did a lifter job to get rid of my loud constant ticking noise,
my no.1 suspect was lifters, and it was.. my noise are gone.

naf, I believe on what u say too, that the cause is most likely related to what I've done in the last job and not something that was doing fine before muy last job.

my car does have 195k miles on it, so yeah its a tired engine but
it never ran rough on hot idle before so Im hoping its not low compression or something..


I did suspect the ECT, that was my very first attempt, I thought I broke them while I was taking apart my manifolds, so I put a new one in
and still does the same.

in cold start engine idles high like it supposed to,
but also even when its warmed up enough to have regular 750-800rpm idle,
it still idles fine.
its when it pass 160F starts bogging, and after that its a matter of time to get worse.

Im gonna open my cover and loosen up my rocker by 1/2 or so to see
whats up now, thanks for all ur help ppl

Gumby

Wonder if yo ugot a cracked head, or intake or..... only when up to temp does the crack exapnd enough to ruin your day.

Would need temp of 240-260 to really hinder any performance.
Stock temps is around 220

That or a bad ICM in your dizzy. When bad they get funky with heat. Gotta make sure and use some heatsink grease with them so they cool right.

sogabe

I bet its something with the distributor!!! damnit

I loosened the rocker arm today even until it had some valve lash left,
I still dont get ticking noise due to my new lifters, but the temp is still reading like a dumbo and gets dumb idle when past 160F..

is ICM easy to replace?
I didnt know they need to be lubed.
Im really new to cars stuff, I read a lot and learned a whole bunch about cars
and now I can call myself a little DIY shady home mechanic
but distributor related stuff is one of my 'i have no clue' area..

is ICM the one that controls the timing advance and stuff like that?

thx for ur info gumby

sogabe

I just did a lot of reading, and I found an interesting article saying
that EGR keeps the combustion chamber temperature cool.

could my egr be stuck open or something giving me rough idle
and overcooled temp reading?

Gumby

Unles your temp gauge is wrong and 160 is really 260.

Stock temp is over 200, so you shouold get to 200F pretty easy.
If its stopping on 160, probably really 260. Bad gauge or sending unit.
Could be some cheap $20 triple gauges to hook up.

Now with mods I have mine running 185-190 constant....
but it won't run them lower temp without em.
You should see more then 160 easy.

ICM controls some of that, so does the computer n such. But when they fail they can get flaky with heat. autozone or other can test the ICM if you pull it me thinks. Its under the rotor in the dizzy.
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N a bad EGR won't have them kind of effects. Something else.

naf

iTrader: (7)

EGR cools combustion temps to allow higher ignition advance at cruise with consequently lower emissions and improved fuel economy. If the valve is opening at idle (it's not supposed to) it could cause rough running. This is unlikely your problem though.

The ignition control module will usually not cause idle problems when it warms up. It either works (engine runs) or doesn't (engine does not run). Heat related failure is 99% of the time defined by failure to start after heat soaked - drive the car, park it for about an hour, icm heats up, car won't start until it cools).

Look at the basics. When you swapped lifters you removed the dist (check timing), the intake (check for leaks) and all the little vaccuum lines (check for leaks), etc.

sogabe

thanks guys.

intake has no leaks as far as I know, I still see the sealants intact when I look through middle manifold passage.

now after my lifter job I couldnt get my car started so I took it to a mechanic,
he said the distributor was inserted backward(180degree off or something?)
and that he fixed them.

but now my plug wire order differs from what it looks from my hayness manual,
all the plug wires goes to different spot!?
it runs like that so it should be in right order I guess but what did they just do..?

I used the timing light and the timing is 2degree advanced, which I believe its within spec right?


it seems to me something is just preventing the computer from going into closed loop.. I wish i had a fancy tool I can hook up to ICM and know wth is wrong

thanks for advice guys.

86camaro383

iTrader: (3)

dont worry about the wires on the cap. Chances are he put it in with a cylinder on top dead center, and put the wires on clockwise in the fireing order, so it looks like its complelty wrong buts its right.

As far as that fancy tool you need, its a scan tool, and you have it, you just dont know it.


Its a paper clip.

I wont tell you how to do it, but

sogabe

hey, I know the paper clip method lol
its just that I dont have any service engine light on, so that wont give me anything.

the fancy scan tool Ive seen will tell u exactly what computer is doing,
that way I will know why my ecm is not going into open loop!

Randy92Z

iTrader: (3)

When you checked your timing, did you disconnect the EST wire? Im not sure about V6 cars but the V8's have this. Did your mechanic forget to re-connect this wire? I know my car runs like crap when its not connected. You should set a EST code (SES light) if its left unplugged. But like I said, Im not sure if the V6 cars have this or not. I noticed you said you dident have any codes. Your base timing setting should be in your manual, as well as your underhood emmissions sticker too.

naf

iTrader: (7)

If you think your cts is not sending an "engine warm" signal to the ecm you can remove the connector and short the two leads. This will send a low voltage signal (temp high).

If you're unsure whether the ecm is in open/closed loop you can try the Field Service Mode (although I've never tried it on a six). From one of the manuals:

"FIELD SERVICE MODE

On fuel injected models, if the ALDL terminal B is grounded to terminal A with the engine running, the system enters the Field Service Mode. In this mode, the MIL will indicate whether the system is operating in open loop or closed loop.

If working in open loop, the MIL will flash rapidly 2 1/2 times per second. In closed loop, the flash rate slows to once per second. Additionally, if the system is running lean in closed loop, the lamp will be off most of the cycle. A rich condition in closed loop will cause the lamp to remain lit for most of the one second cycle.

When operating in the Field Service Mode, additional codes cannot be stored by the ECM. The closed loop timer is bypassed in this mode."

Just don't start it with the terminals grounded.

sogabe

thanks all for ur advice!!

yeah the 6 has EST connector too, I disconnect them everytime I mess with timing.

I think I solved half my problem.
I loosened all my rocker arm by 1/2 turn,
some went loose to a point where I can move the rocker a bit,
but I thought to myself, the heat should take care of the gap..

now I dont have rough idle anymore ,
but my second half problem remains the same!!

my temp reading never goes above 160, no matter what!! and I know the car IS going over 160
so Im scared it might overheat without me knowing, so in town driving I have to keep my a/c on to prevent overheating and im freezing..


could this be the thermostat? what happens if the thermostat isnt for my car or something? I read somewhere that it could cause wrong temp reading but how so?
i think even if it was stuck open wouldnt it go over 200 easily in town?

or could it be that, I still have mechanical problem where the ECM has to do some compensation by going into closed loop?
at hot idle, I do feel a very slight small stumble but its not really that noticable
and Im not sure if ecm is kicking in to compensate or something.

so much u all rock man u guys been so helpful so far.
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and thanks naf for that tip.
by "just dont ground it before starting",
is that mean I have to ground A and B after the car is started?

thanks!

Black85Z28

You've got it backwards, you need to have the heat on to keep the engine cooler. It draws heat away from the engine and blows it towards you.

Just go to your local auto parts store and install a new temp gauge to eliminate that possibility.
cheap sunpro gauges ftw

Gumby

Yep your temp gauge is F'ed in any case, so change it with out haste.


thermo stat wont do anything but stick, but car shouls boil over if its that hot. but still. There is no way your only running at 160f, so just do the temp thing first. Heat kills fast.

naf

iTrader: (7)

Keep in mind that the sender for the dash temp guage is different from the CTS for the ECM. On a V8 the temp guage sender is on the driver's side cylinder head. Check the location for the sender on your six and make sure the single wire is connected.

When grounding the ALDL you want to do it after the engine is running or with ignition on/engine off to pull codes. Never attempt to start engine with ALDL grounded.

sogabe

ay naf.. if I ground it then start the car what happens..?

I think Ive done it once before and didnt work so I pulled the clip out,
but did I just screw my ECM there? thanks

naf

iTrader: (7)

It can damage the ECM but if it kills it, you'll know. The ECM will generally either work or not work so don't worry about it.