gabrielzzz

this problem has been plagueing my car ever since i owned it. the symptoms are, when i idle the car, it runs slightly ruff, and after i push the acceleration, even a little, it starts to bog, i can hear pressure build up through the air intake, until the pressure builds so much that i hear a pop noise throught the air intake....this problem is getting worse and worse, now i cant drive it out of my driveway, my thought, could it be the cat? just seems like there is pressure build up somewhere, or could it be the wastegate for the turbo, this is a 1982 280zxt coupe, 170,000 miles, someone help me....PLEASE, i dont want to send it to the rusted gates of the wrecking yard, but i cant drive my dads car to work every day.

NismoPick

have you checked your air/fuel ratio? I had that same prob when I first built my L28ET... It would idle ok, but when I'd jump on the throttle, it would just bog like crazy, even when the turbo started to spool. Found out I had a clogged injector. I discovered it by pulling the sparkplugs.... 5 of the 6 were showing wear, the 6th was still brand new looking.... pulled the rail & after testing that injector, realized it wasn't spraying.

Start by pulling the plugs... see if they are the same, then report back.

nismo619

i have a 1982 280zxt that when i started it , it would run like crap. But after i took up the rear carpet and pulled out the FEUL sender unit and wiggied it loose from the fuel tank and cleaned the little screen on the fuel sender to the fuel pump.. i changed out everything the fuel filter new fuel injectors and that fixed my problem i hope i can help u out more p.s. u might want to try an use some CARB cleaner and clean the MASS AIR SENSOR and the THORTTLE BODY as well its a eazy job. p.s. let me know if any of this works as it worked for my 82 zxt 2+2

p.s. get a 10mm socket and a 17 mm open end wrench and take off your CAT to see if its cloged just hold it up to the sun to see if u can see through it... bets are its not your CAT at all p.s. start with the basics fuel injection ;-)

gabrielzzz

well, this is the list of things ive already done to the car, i have replaced all injectors, all injector connectors, all spark plugs (ngk plugs) spark wires (ngk wires) replaced the fuel dampener that was bad, and also did the AFM fix that J put up, also replaced the valve cover gasket (doesnt have to do with it i dont think) and thats about it, im left with maybe the fuel screen fuel pump or the cat, or maybe the turbo wastegate...?

p.s. tried to take off the cat but i dont have a torch and broke one bolt, tood two more bolts off, and stripped the last one, so cant get the damn thing off to see if that is it or not, i have an appointment this coming monday at this place called Zworld off of the Pacific Coast Highway, hopefully they will give me an honest answer.

lww

It's not your waste gate. That will have no effect on low end unless it's actually opening too soon which wouldn't give you the symptoms you're currently experiencing.

How's your timing look? Mechanical and vacuum? I'm thinking it's either your TPS or your timing is off and probably too retarded.

Do you have a timing light? If so, disconnect the vacuum hose from the vacuum advance on your distributor and check your mechanical advance.

Do you have a Factory Service Manual?

NismoPick

It's a 280ZXT, so it doesn't have vac advance. You need to unplug your TPS when you time it. Set it to 20 degrees if it's different.

lifegrddude

Change out the ecu connectors. They go bad and will cause what you're describing. I had to change mine out because it got to the point where I had to wiggle them into a certain position to get the car to drive right. It's most likely the top harness connector to the ecu that needs to be messed with. Wiggle that connector while driving and see if it clears up when you have the wires a certain way. I eventually changed out the connectors for some off of a Z31. I haven't had the problem since then.

RodMoyes

What ever you do, just don't give up so easily. It's a 20+ year old car, and it's going to have a few hick ups. For the most part though, these things are very reliable. It's almost always going to be something relatively small and inexpensive that bites the hardest and is the most difficult to figure out. Just have a little more patience and perseverance and you'll be just fine. I don't know alot about the L28ET so I'm going to let these guys walk you through it. Just don't throw in the towel quite yet. I gaurantee you it will be something small and easy to fix. LifeGuard's advice seemed pretty good. Also, I know you did the AFM rebuild, but that may still be acting up. I did the AFM thing and it cleared up all my problems. A few day's later though, they started to come back. It turned out that I hadn't cleaned the connectors where it plugs into the base good enough. I pulled off the plug and cleaned it up really good and it went back to being just fine... Once again, it was a very small thing. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... Rod.

gabrielzzz

these are all great tips, my thoughts on the timing might be it, i was thinking about it, but would the timing go out gradually, without me even touching a single thing on it? and would it fix itself and start to mess up again? ill check the ECU connectors and the TPS....the thing is, i can bearly keep it running to wiggle the connectors, but ill give it a go, i might not be the brightest person for asking this, but what exactly is a TPS? ive decided ive put too much blood sweat and tears into this car, including money, so im not going to give up, that would be like throwing away my money, if i cant figure it out by this weekend, i have an appointment this weekend, and then ill know for sure what the problem is. thanks again for the help

gabrielzzz

i also need a factory service manual....BADLY!

lifegrddude

TPS is the throttle position sensor, it's the black box attached to the throttle body. Another thought on your problem might be a vacuum leak. Double check all the vacuum lines (I know, it's like 5 miles worth of lines haha) When I first bought my zxt, the PCV valve hose was practically non-existant from erroding. Also check the fuel pressure, it should be about 30psi. Since you said the car has 170K on it, the pump could be on it's way out. Did you also replace the fuel filter? Check the gas tank for debris, it's possible there's a build of crud in there that's blocking off fuel flow too.

gabrielzzz

well, my PCV hose i cracked at the base, i shortened it and stretched it to the valve cover, still a crack, but needs replacing, i replaced the fuel filter about a month ago, but ill unplug it and blow through it and see if its plugged. i dont have a fuel pressure gauge at the moment, and the fuel pump may be the problem but would low fuel pressure make that pressure building problem i hear, along with the popping noise?

lifegrddude

Backfiring through the intake is a lean condition so it's possible low fuel pressure will cause that to happen, but you'll need a gauge to verify you're getting the right pressure.

gabrielzzz

then its time to rent a gauge from autozone

efrain

verify the lines that goes in and out of the fuel pressure regulator

jfairladyz

Intermittent problems are almost always electrical. The popping noise you hear through your intake can be one of two things. Either a backfire (through the intake) or the flapper door in the AFM. I doubt it's a clogged cat causing your problem. Not if it's to the point where you can't even drive it out of the driveway. I'd check the timing and make sure thats all good. The other thing I'd point my finger out in your case would be the AFM. Pull off the intake tube and make sure the flapper door operates nice and smoothly. Other than that I'd start cleaning connectors and checking them for looseness or corrosion.

hoov100

have you checked the valves? a build up of presure in the intake may be a stuck intake vavle.

NismoPick

I'm gunna have to nix that one... lets start w/ basics before tearing down the head here.

gabrielzzz

alright, last night i checked the AFM for a third time, used a razor to clean the contacts, and lubricated the door, opens like brand new, made sure the chip is in right position, and didnt slide around or something, adjusted the gate spring 3 clicks looser...no change, i checked the ECU harness, all connectors look good, joggled them around a little and those are good, and from what i see, the TPS is working, but how exactly do you check the TPS?

gabrielzzz

the last thing i have to do is check the timing, counter clockwise is higher rpm's right? should i start twisting the distributor around and see if thats it? as of now, the distributor is maxed out to the clockwise position.

NismoPick

You do have a timing light right? If you've played w/ L28ET's for about 10 years, you can prolly set the timing w/o a light.... but if you're having probs, make sure it's done w/ a light. Make sure the TPS is unplugged while timing, as the ECU adjusts timing partly through the TPS.

Have you pulled the sparkplugs yet to look at them? (I believe I posted that the other day)

gabrielzzz

my question is, if it backfires through the air intake, would that still mean the timing is off??
if the timing is off, it would backfire through the exhaust right?

gabrielzzz

actually i forgot that one, tonight ill pull the sparkplugs and let you know what they look like.

CWHammer

Shoot me an email at hammershotwheels@comcast.net, I can help you out with the manuals.

Craig

gabrielzzz

cool, thanks, emailed you about the manuals