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1G Just got a 90 Laser RS turbo breaking up at 5k

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Lazer owner at 15

Probationary Member
13
6
Jun 7, 2023
Waterloo, New_York
i just got a 1990 Laser RS turbo it has had problems around 5k rpm with the engine cutting power for a split second. i was hoping to get help with this and i was wondering what the most appropriate forum section would be
 
Have you done any maintenance at all? What is done to the car? Please fill out a profile as best as possible and let us know the status of the car.
Maintenance?
Compression check?
Fluids?
What have you done so far?
We don't have enough information to objectively help you. We would be guessing.


From your screen name I'm guessing you're 15? We all have to start somewhere. Help us help you.
 
Have you done any maintenance at all? What is done to the car? Please fill out a profile as best as possible and let us know the status of the car.
Maintenance?
Compression check?
Fluids?
What have you done so far?
We don't have enough information to objectively help you. We would be guessing.


From your screen name I'm guessing you're 15? We all have to start somewhere. Help us help you.

have not done any maintenance to it just got it a bit ago and i don't even have a license yet

yes i am and thank you for trying to help me I'm new to all this forum and car stuff
 
have not done any maintenance to it just got it a bit ago and i don't even have a license yet

Let's assume for now the car is stock. Plugs and wires are a common problem. If maintenance us unknown I'd start there. Most of us swear by NGK products. Stock plugs are NGK bpr6es. NOT bpr6es-11.

I'm a cheap bastard and buy cheap wires. Rockauto.com is very cheap for these type of items. Watch the shipping.
BTW my kids are older than you. Keep asking questions.

Just read your profile. Given it had mods before I would verify everything. Do not trust something has or has not been done unless you look yourself.

Does the car have a boost gauge? If so what does it read? Stock boost is 11. ECU cuts boost for any reason it will be 8. This is assuming you have stock parts. I would doubt it.
 
Let's assume for now the car is stock. Plugs and wires are a common problem. If maintenance us unknown I'd start there. Most of us swear by ngk products. Stock plugs are ngk bpr6es. NOT bpr6es-11.
I'm a cheap bastard and buy cheap wires. Rockauto.com is very cheap for these type of items. Watch the shipping.
Btw my kids are older than you. Keep asking questions.
ok i will check that thanks

Just read your profile. Given it had mods before I would verify everything. Do not trust something has or has not been done unless you look yourself. Does the car have a boost gauge? If so what does it read? Stock boost is 11. Ecu cuts boost for any reason it will be 8. This is assuming you have stock parts. I would doubt it.
i haven't checked for other mods so far but it dose have stock boost gauge im almost positive it read higher that 11 psi
 
i haven't checked for other mods so far but it dose have stock boost gauge im almost positive it read higher that 11 psi
Stock boost gauge doesn't measure boost and it doesn't have a scale. It's an estimate based on airflow. It's not to be trusted. If it pegs out in the cars current form that is definitely a problem and usually indicative of an air leak after the turbo known as a "boost leak"
If you haven't already check out the resources page on this site. You will find common problems and catch up on 30+ years of resarch.
 
Stock boost gauge doesn't measure boost and it doesn't have a scale. It's an estimate based on airflow. It's not to be trusted. If it pegs out in the cars current form that is definitely a problem and usually indicative of an air leak after the turbo known as a "boost leak"
If you haven't already check out the resources page on this site. You will find common problems and catch up on 30+ years of resarch.
ok thank you i was wondering if that was the case because it seemed like i was having a fuel cut at 5k rpm and one of the causes of fuel cut was boost leak

is there an engine position where all intake valves are closed to test if there is boost leak
 
ok thank you i was wondering if that was the case because it seemed like i was having a fuel cut at 5k rpm and one of the causes of fuel cut was boost leak

is there an engine position where all intake valves are closed to test if there is boost leak
Yes you could be looking at fuel cut. If you have a leak. At stock boost you wouldn't when you are leak free. Looks like you've read up on fuel cut. Fuel cut feels like a brick wall. Car cuts off hard. Bad plugs and wires car just breaks up.
 
Yes you could be looking at fuel cut. If you have a leak. At stock boost you wouldn't when you are leak free. Looks like you've read up on fuel cut. Fuel cut feels like a brick wall. Car cuts off hard. Bad plugs and wires car just breaks up.
yes when it cuts out it cuts out hard and it only cuts out on medium to hard acceleration in high boost zones of rpm (if that makes since) witch leads me to believe more that its fuel cut
 
Keep pushing forward. On a car that old a visual inspection may find something. Check clamps etc. Stock intercoolers are known to corrode under the hose depending on where the car is. Definately in salt states.
The boost leak test revealed some major and minor leaks some of which are fixed (injector seal kit + large intercooler leak). It still has the cut off but it has changed into a weaker cut which I believe is best described as the spark breaking up, still only around 5K rpm under high load but no more hard cutoff.

I'm planing on checking coils because I have already replaced spark plugs and wires and still no change to the problem. I did do a fuel pressure test to rule out any fuel problems
 
Last edited by a moderator:
The boost leak test revealed some major and minor leaks some of which are fixed (injector seal kit + large intercooler leak). It still has the cut off but it has changed into a weaker cut which I believe is best described as the spark breaking up, still only around 5K rpm under high load but no more hard cutoff.

I'm planing on checking coils because I have already replaced spark plugs and wires and still no change to the problem. I did do a fuel pressure test to rule out any fuel problems
Did this car sit fir awhile.
Does it have fresh gas?
 
I was just about to mention fuel. Replace the fuel filter and get your injectors cleaned. What did your old spark plugs look like when you replaced them? Take a look at your knock sensor, is it oozing or obviously damaged? Sensitive knock sensors can pull timing at certain harmonics or whenever they feel like it.

It wouldnt hurt to pull your upper timing cover and line up your timing marks just as a sanity check. Strange things happen when you're a tooth off.

Keep us updated and dont get discouraged if you encounter a "grumpy forum old timer", they mean well but are not well socialized. ;)
 
It does sound like he is hitting fuel cut. Does it feel like it hits a wall, then back to normal? I was 19 first time I felt that, definitely a worrying feeling.
I'm no expert, but I would search for a manual boost controller, maybe someone tucked one away somewhere, and check the wastegate for normal operation, at a point the stock fuel delivery can't keep up with the boost and if you can turn it back to normal levels it should stop doing that, and at least if it does at normal boost you will know to look elsewhere.

Oh yea, one of the first things you should.buy and install, is a proper aftermarket boost gauge.
 
The boost leak test revealed some major and minor leaks some of which are fixed (injector seal kit + large intercooler leak). It still has the cut off but it has changed into a weaker cut which I believe is best described as the spark breaking up, still only around 5K rpm under high load but no more hard cutoff.

I'm planing on checking coils because I have already replaced spark plugs and wires and still no change to the problem. I did do a fuel pressure test to rule out any fuel problems
I would fix the boost leaks first. That air has been accounted for by the MAF and the ECU is adding fuel for air that is no longer there. This could have the same effect as having a boost controller running higher than stock boost and causing the stock fuel system to hit fuel cut. All the other stuff is important too, you need good compression, good ignition, and a clean fuel system, but if you know you have boost leaks, I would finish addressing them before chasing anything else.
 
Did this car sit fir awhile.
Does it have fresh gas?
no i drive it as a summer car and the problem continues no matter how much i drive it

It does sound like he is hitting fuel cut. Does it feel like it hits a wall, then back to normal? I was 19 first time I felt that, definitely a worrying feeling.
I'm no expert, but I would search for a manual boost controller, maybe someone tucked one away somewhere, and check the wastegate for normal operation, at a point the stock fuel delivery can't keep up with the boost and if you can turn it back to normal levels it should stop doing that, and at least if it does at normal boost you will know to look elsewhere.

Oh yea, one of the first things you should.buy and install, is a proper aftermarket boost gauge.
it used to feel like a wall before i fixed some boost leaks but now it isn't as hard but cuts out Alost like its running out of spark at the higher rpm and under high engine load, the car is completely stock accept for a 3in turbo back exhaust and I'm in the process of putting an aftermarket manifold on as we speak so there's no aftermarket boost controller.

I would fix the boost leaks first. That air has been accounted for by the MAF and the ECU is adding fuel for air that is no longer there. This could have the same effect as having a boost controller running higher than stock boost and causing the stock fuel system to hit fuel cut. All the other stuff is important too, you need good compression, good ignition, and a clean fuel system, but if you know you have boost leaks, I would finish addressing them before chasing anything else.
the only boost leak that i haven't fixed and i know of is a leak around the throttle body witch doesn't seem that major, with that being said i will still reseal it i was just wondering if it could be something else because it doesn't seem like fuel cut to me but I'm also no expert and am not ruling fuel cut out
 
it used to feel like a wall before i fixed some boost leaks but now it isn't as hard but cuts out Alost like its running out of spark at the higher rpm and under high engine load, the car is completely stock accept for a 3in turbo back exhaust and I'm in the process of putting an aftermarket manifold on as we speak so there's no aftermarket boost controller.
Does it have a real boost gauge? 3" turbo back is known to cause boost creep/overboost. You need to know for sure.
 
thank you for the suggestion of over boosting i stopped up at STMtuned and picked up a fp cast race manifold (i know the extra flow from the manifold wont help with my issue) and they basically conformed the idea of it being over boos because of the extra flow on the exhaust side, i have decided to wait for winter to send my ecu to get a socketed eprom installed because my ecu curranty docent have it, i will also wait till the winter to install a wideband because i would like to drive it during the summer even though i will have to keep it out of the high end.

thank you again for you're help and the suggestions
 
thank you for the suggestion of over boosting i stopped up at STMtuned and picked up a fp cast race manifold (i know the extra flow from the manifold wont help with my issue) and they basically conformed the idea of it being over boos because of the extra flow on the exhaust side, i have decided to wait for winter to send my ecu to get a socketed eprom installed because my ecu curranty docent have it, i will also wait till the winter to install a wideband because i would like to drive it during the summer even though i will have to keep it out of the high end.

thank you again for you're help and the suggestions
Neither of those will fix that problem. Different wastegate will fix it.
 
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