bauermd

1988 L98 AT 92k Miles - Headgaskets done 15 months ago by previous owner. Brand new plugs/wires/cap/rotor about 500 miles ago.

Car developed a bad deadspot when you push the gas down suddenly, no matter what speed. If I am at a complete stop and go half throttle suddenly, the car will bog down and die immediately. If I ease into the gas, it runs fine, WOT and upper RPMS are fine also. No codes thrown, and car starts fine every time.

I chucked it up to a faulty TPS, but checked and verified .54, and smooth climb to 4.2 at WOT.

I recently did a TB service with new gaskets and reused the IAC and TPS. Changed to a 160deg thermostat at the same time. Car ran fine for the first 50 miles or so.



So jump to this morning, was 35 degrees out, started car and left for work. About 1/2 mile down the road I noticed temps climbing FAST. I turned around and drove back home. Temps were showing at 235-245 and my low coolant light came on. Popped the hood and my coolant reservoir was packed full. The coolant was not actually hot, just had little to none in radiator anymore. I popped the radiator cap and the reservoir bubbled.

I do not have smoke on startup or anytime during driving. No leaks in the driveway, and no leaks during this occurrence.

So my question is, could the cold weather of caused this? Maybe a relation to the deadspot upon pressing the pedal? Just hard to believe a headgasket pressurizing my system... well I am hoping not.

Tom400CFI

Cold weather would not be the cause of this. It's possible that your T-stat is stuck closed and you boiled coolant in your engine...pushing coolant into the overflow. Probably not likely, though.

I'd go buy a HC test kit from an auto parts store and test for hydrocarbons in your coolant.

Kevova

I think you may have 2 different conditions going on. You did install thermostat correctly with larger half in intake manifold? I would also check fuel pressure or if no gauge available replace fuel filter.

bauermd

Thermostat is in correctly, gasket looks ok. Car drove fine for a few days after that install, as temps stayed within range.

Fuel filter was replaced approx 2 weeks ago.

Today I am going to empty overflow tank, re-burp the system and check to make sure my coolant by-pass didn't suck air in or something and blow the coolant out to the overflow. Also check the rad cap to make sure its still in good order. It's hard to believe its a HG, when it was replaced 15 months ago and car did not overheat. Happened this morning before the car even got out of the neighborhood.

desertmike1

Both of your symptoms can be a direct result of a leaking Head gasket! Besides an Hydrocarbon test; you could also pull the spark plugs and do a Visual Exam..

The system does not need re-burping! self bleeding..

antfarmer2

Do a pressure test on the system and hope it is a leaky hose or bad cap make sure you look at the hose going to the tank.

bauermd

That's what I am hoping. I did a coolant bypass when I serviced the TB so maybe one of my jumper connections bit the dust and sucked air in or something. No leaks visible though.

bauermd

got home today and checked a few things. Half of the coolant got sucked back into the radiator so now only half the coolant tank is full, but I added some this morning so that's normal I guess. Checked radiator cap, and all hoses. Started car and it acted completely normal, no coolant moved, temps rose fine and no smoke or anything.

Tom400CFI

When I was in automotive school, classmates would frequently ask about obscure, odd-ball problems about their cars, similar to this one...that there was no way the prof could answer w/o looking at the car in person. His bland, flat response was always the same, and it jumped to mind after your last post. He'd respond with mono tone;

"AM, FM.........AutoMotive Fuggin Magic".

Hopefully it continues to run trouble free now.


.

bauermd

It still falls on its face when I hit the throttle in drive. But the coolant isn't an issue as of this afternoon.

Tom400CFI

I'd have started by checking the TPS...but you did that already. Good 1st move there. Since you've checked it, I'd start by checking fuel pressure.

antfarmer2

and how old is your o2?

bauermd

I was suspecting a failing O2, but the problem is getting more significant. It only did it a few times the first day, now it does it almost everytime I hit the gas. It will do it upon the first start of the day, so in open-loop which I believe rules out an O2 problem? Car pulls completely fine once the initial surge happens, all the way to WOT it pulls fine. Just the initial throttle hit it wants to die unless I feather into it.

antfarmer2

How is the fuel pressure? Pull the vacumm line off the fpr and smell for fuel.

bauermd

I am going to check FP today, and check FPR for fuel. Just odd that after the initial stumble, acts completely fine through the RPMs.

antfarmer2

Not if it is flooded check your oil for fuel do not want a grenade.

bauermd

Even if I am doing 10mph cruising and hit the gas, it will do the same thing, kind of like when I hit the gas, it cuts all fuel out and then picks it self up and goes fine. haha I love car problems

Also, noticed the TV cable has almost 0 tension, is loose and car shifts extremely early.

antfarmer2

Sounds like three problems to me.

Kevova

You definitely want to make sure TV cable is set correctly. Do you have access to scanner? Does vacuum to MAP sensor respond instantly with throttle? It should head toward 0 as soon as throttle is cracked.

bauermd

I am going to set the TV cable to the best of my knowledge today. Car is shifting super early, so that is probably out of adjustment from messing with the TB.

I do not have a scanner. If I connect a gauge to read vacuum, I should be sitting above 14 at idle, and then move towards 0 when I introduce throttle correct?

Going to test injectors today for resistance also.