Engine Cutting, Stuttering, and Hesitating
02-20-22, 04:44 PM
#1
Junior Member
Thread Starter
Engine Cutting, Stuttering, and Hesitating
I've got a 1991 NA Manual.
WHATS HAPPENING
My engine recently began acting oddly. There seems to be three levels of symptoms. The worst it gets is the engine will cut out completely, stop running. It catches back in a second or less. Behind that the engine will stutter seeming to cut and catch repeatedly very quickly. And more subtly sometimes the engine simply seems to reduce in power a bit and then come back. It often will do at least one of these when acceleration whether accelerating slowly or quickly. It also does it when it's just cruising and it has done it on deceleration as well so pretty much anytime this can happen but almost always happens when accelerating. The engine is also idling oddly. It seems to be hovering as low as 500 RPM which is noticeably lower than it used to and when the engine is cold it won't idle without maintaining some throttle on it.
WHATS BEEN DONE
The fuel injectors were replaced not that long ago. It seemed like a fuel issue to me so I replaced the fuel filter and nothing changed. Some people in another thread seemed to experience similar issues and fixed it by cleaning the fuel strainer at the bottom of the fuel pump so I took a look at that. It was falling apart so I replaced the pump and the strainer which also didn't seem to even affect the issue. Due to the lack of a working O2 sensor the engine has been running rich (you could smell it) so I checked the spark plugs and they seemed dirty so I cleaned them and nothing change. So I replaced the plugs entirely and again, nothing changed. I resistance check the spark plug wires and they checked out. I've also replaced the o2 sensor. I've run injector cleaner through it a few times as well. Nothing I've done has seemed to even change the problem.
WHAT HAPPENED LATELY
Nothing that happened recently with the car I can clearly connect to the issue. The car sat for a couple week while I put a new dashboard in and a bunch of interior stuff that's all that happened recently. As mentioned before it's been running rich for a little while but I've since fixed that issue.
I'm not sure what to check/try next that's why I've come here. Thanks in advance.
WHATS HAPPENING
My engine recently began acting oddly. There seems to be three levels of symptoms. The worst it gets is the engine will cut out completely, stop running. It catches back in a second or less. Behind that the engine will stutter seeming to cut and catch repeatedly very quickly. And more subtly sometimes the engine simply seems to reduce in power a bit and then come back. It often will do at least one of these when acceleration whether accelerating slowly or quickly. It also does it when it's just cruising and it has done it on deceleration as well so pretty much anytime this can happen but almost always happens when accelerating. The engine is also idling oddly. It seems to be hovering as low as 500 RPM which is noticeably lower than it used to and when the engine is cold it won't idle without maintaining some throttle on it.
WHATS BEEN DONE
The fuel injectors were replaced not that long ago. It seemed like a fuel issue to me so I replaced the fuel filter and nothing changed. Some people in another thread seemed to experience similar issues and fixed it by cleaning the fuel strainer at the bottom of the fuel pump so I took a look at that. It was falling apart so I replaced the pump and the strainer which also didn't seem to even affect the issue. Due to the lack of a working O2 sensor the engine has been running rich (you could smell it) so I checked the spark plugs and they seemed dirty so I cleaned them and nothing change. So I replaced the plugs entirely and again, nothing changed. I resistance check the spark plug wires and they checked out. I've also replaced the o2 sensor. I've run injector cleaner through it a few times as well. Nothing I've done has seemed to even change the problem.
WHAT HAPPENED LATELY
Nothing that happened recently with the car I can clearly connect to the issue. The car sat for a couple week while I put a new dashboard in and a bunch of interior stuff that's all that happened recently. As mentioned before it's been running rich for a little while but I've since fixed that issue.
I'm not sure what to check/try next that's why I've come here. Thanks in advance.
02-23-22, 10:45 AM
#3
Junior Member
Thread Starter
2. I don't have a tester but I pulled the plugs and listened and I'm getting 3 puffs in each housing so I have compression can't say how perfect it is. But the plugs are nasty.
The plugs were new ~250 miles ago. Has to be related to my issue but I'm not sure if this is the cause or a symptom.
Last edited by The_Pied_Shadow; 02-23-22 at 10:55 AM. Reason: smaller image
02-23-22, 11:45 AM
#4
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check the codes? if there are any it would point you in a direction
02-28-22, 01:38 PM
#5
Junior Member
Thread Starter
Following trouble codes:
- 09 - Water Thermosensor - Coolant temp fixed at 176F
- 11 - Intake Air Thermosensor (Engine) - Intake air fixed at 68F
02-28-22, 02:14 PM
#6
Rotary Freak
Following trouble codes:
- 09 - Water Thermosensor - Coolant temp fixed at 176F
- 11 - Intake Air Thermosensor (Engine) - Intake air fixed at 68F
When this happens the ECU is designed to assume a set temp (as the code implies). This temp is "warmed up." When the car is cold and you try to start it, it will be running way lean because instead of detecting that it is cold and applying warmup enrichment it will assume that the car is already warm.
I don't know how much of an effect this has once the car is warmed up, but it's certainly a good starting place to inspect / replace that sensor before proceeding. Stand by the passenger side fender and lean over the engine with a flashlight. Look straight down behind the alternator, it looks like an injector connector and it should be firmly plugged into the sensor on the back of the water pump housing.
The second one is less concerning since the ECU only uses it for bypass air IIRC (the other intake temp sensor in the AFM is used for injection). Anyways, it could certainly affect the warm idle because it is affects BAC valve duty but it likely isn't the main problem. I'd definitely replace it anyways, but the first code is the real issue.
After replacing those sensors see what happens. That may be all you need to do, or there may be more required (setting TPS, etc). The sensors are the first task.
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The_Pied_Shadow (02-28-22)
02-28-22, 03:04 PM
#7
Junior Member
Thread Starter
The first code is the big problem, it means either the coolant temp sensor is disconnected or has failed. I'm leaning towards disconnected because you said you replaced the injectors and this is in the area.
When this happens the ECU is designed to assume a set temp (as the code implies). This temp is "warmed up." When the car is cold and you try to start it, it will be running way lean because instead of detecting that it is cold and applying warmup enrichment it will assume that the car is already warm.
I don't know how much of an effect this has once the car is warmed up, but it's certainly a good starting place to inspect / replace that sensor before proceeding. Stand by the passenger side fender and lean over the engine with a flashlight. Look straight down behind the alternator, it looks like an injector connector and it should be firmly plugged into the sensor on the back of the water pump housing.
The second one is less concerning since the ECU only uses it for bypass air IIRC (the other intake temp sensor in the AFM is used for injection). Anyways, it could certainly affect the warm idle because it is affects BAC valve duty but it likely isn't the main problem. I'd definitely replace it anyways, but the first code is the real issue.
After replacing those sensors see what happens. That may be all you need to do, or there may be more required (setting TPS, etc). The sensors are the first task.
When this happens the ECU is designed to assume a set temp (as the code implies). This temp is "warmed up." When the car is cold and you try to start it, it will be running way lean because instead of detecting that it is cold and applying warmup enrichment it will assume that the car is already warm.
I don't know how much of an effect this has once the car is warmed up, but it's certainly a good starting place to inspect / replace that sensor before proceeding. Stand by the passenger side fender and lean over the engine with a flashlight. Look straight down behind the alternator, it looks like an injector connector and it should be firmly plugged into the sensor on the back of the water pump housing.
The second one is less concerning since the ECU only uses it for bypass air IIRC (the other intake temp sensor in the AFM is used for injection). Anyways, it could certainly affect the warm idle because it is affects BAC valve duty but it likely isn't the main problem. I'd definitely replace it anyways, but the first code is the real issue.
After replacing those sensors see what happens. That may be all you need to do, or there may be more required (setting TPS, etc). The sensors are the first task.
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03-02-22, 12:03 PM
#8
Junior Member
Thread Starter
So I found the plug. It appears as though the plug itself (not the sensor) is damaged and thus it has wiggled loose. I pushed it further on and it seems to have fixed both issues.
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The_Pied_Shadow (03-02-22)
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