4age bogging and starting issues

[NZWAKA]

Hi guys,

New to the forums, basically I have this 1990 AE92 FXGT I bought about 6months ago and it has developed a starting and bogging issue under load.

The problem:
The car seems to have trouble starting, sometimes its fine once its warmed up other times it cranks slowly till it dies, once started it high idles like normal till it reaches optimal temperature then it sits at 800rpm. Once it gets to 800rpm you can hear it missing on idle and between 1-1.5k rpm the car bogs and sometimes gets close to dieing, it's also drinking a lot of fuel. Im only getting around 300k's to a full tank

What I have replaced:
Distributor cap + leads
Spark plugs and gapped according to factory manual specs
Fuel filter
Thermostat
TPS resistance is in within spec
No vac leaks

What I discovered: Servicing history is unknown on this car, the spark plugs were swimming in oil due to rocker cover gasket being shot, so drained it all out, new plugs and replaced the gasket. Fuel filter was absolutely disgusting and looked like it hadn't been changed in years. Distributor was leaking oil so new cap/seal and leads, thermostat was stuck open so replaced that. Coolant system flushed and re bled with toyota green.

Im coming to the conclusion it has clogged injectors after having a look under the rocker cover, it was absolutely caked. Has anyone got any suggestions?

[davew7]

Search DYI injector cleaning. You just need a 9V battery, switch, and a can of carb cleaner, plus a little adapting on the spray hose. I added a lite to the circuit to help monitor the spray time cycle. You may also want to soak the injector fitlers in cleaner. For starting problem, verify you have current at the cold start injector at the 2 pin connector and the other pin goes to ground [ about 8 ohms resistance ]. There is a chances that the injector is shot. When appling voltage to the cold start injector, you should be able feel the coil. Hopefully just cleaning the cold start injector will solve the problem. You need to make a fine threaded adaptor for the cold start injector, because Toyota is VERY proud of their of gold plated cold start injectors. Dave W

[ollie83]

Sounds like your running rich, could be a number of things. Have you run an engine diagnostics test? That might help to guide you if there are any issues/ failures with particular sensors etc.

[rebuilder86]

u say no vacuum leaks but this stinks of a vac leak haha. mostly the idle hesitation, not so much the bogging down, bit possibly of the leak is big enough.
most likely the intake manifold gasket itself.
im curious as to why u said it has no vacuum leaks. have u sprayed ether all around the intake and listened for a changr in rpm?

[Hiro]

it's also drinking a lot of fuel. Im only getting around 300k's to a full tank

What's your definition of a full tank? AE92s (Australian-made ones at least) are notorious for having a 50L tank that can only take ~30-35L. 300k to 35L is still pretty bad consumption for a 4AGE, but it's still way better than 300k to 50L.

[rebuilder86]

yeh ks to the tank means nothing at all, unless u say something like 100 ks to a tank.
:|
poor fuel economy can result from anything, it doesnt help us pinpoint where the problem may be.
just having another read of this, why does gunk in the rocker cover lead u to a dirt fuel injector conclusion?

[NZWAKA]

Sounds like your running rich, could be a number of things. Have you run an engine diagnostics test? That might help to guide you if there are any issues/ failures with particular sensors etc.

I am incredibly busy and just unfortunately haven't had the time, its definitely on the list of things to do as well as a compression test.

u say no vacuum leaks but this stinks of a vac leak haha. mostly the idle hesitation, not so much the bogging down, bit possibly of the leak is big enough.
most likely the intake manifold gasket itself.
im curious as to why u said it has no vacuum leaks. have u sprayed ether all around the intake and listened for a changr in rpm?

You have just answered your own question, I have gone around with a stethoscope it's definitely not a vac leak.

What's your definition of a full tank? AE92s (Australian-made ones at least) are notorious for having a 50L tank that can only take ~30-35L. 300k to 35L is still pretty bad consumption for a 4AGE, but it's still way better than 300k to 50L.

Car has a 50l tank. Trust me fuel consumption is VERY bad, I have now done 420km on a tank and a half, yes yes I know its not an accurate measurement.

[rebuilder86]

stethoscope is really not the best way to chexk for a vacuum leak.
spray some combustible spray like "start ya bastard" all around the throttle body and hoses and manifold gasket while at idle.
it really stinks like manifold leak.
this is a cheap test and id be doing it first.
some ppl use water and listen for a decrease in rpm, but ether is amazing and a tiny drop has a large effect on rpm.
the power on acceleration / bogging issue is a reason to suggest otherwise, like a bad spark. have u checked the quality of the spark from the coil? thats another free test to check.
is distributor mechanical or reluctor type?
if mechanical check points clearance.

[NZWAKA]

Search DYI injector cleaning. You just need a 9V battery, switch, and a can of carb cleaner, plus a little adapting on the spray hose. I added a lite to the circuit to help monitor the spray time cycle. You may also want to soak the injector fitlers in cleaner. For starting problem, verify you have current at the cold start injector at the 2 pin connector and the other pin goes to ground [ about 8 ohms resistance ]. There is a chances that the injector is shot. When appling voltage to the cold start injector, you should be able feel the coil. Hopefully just cleaning the cold start injector will solve the problem. You need to make a fine threaded adaptor for the cold start injector, because Toyota is VERY proud of their of gold plated cold start injectors. Dave W

Thanks for this mate! Very helpfull, will hopefully get it done in the weekend.

[davew7]

Cleaning the injectors is pretty straight forward, adapting a hose and a fitting or two to the spray carb cleaner. The cold start injector is a little harder. I found an old bike carb float check valve that had the same fine threads as the cold start banjo injector fitting. I than epoxied the carb cleaner straw right into the center of the check valve. Probably finding a fine thread fitting will be the hardest part, in cleaning the cold start injector. Dave W7

[ollie83]

I really think before investing time in cleaning the injectors, you should run a diagnostic test. It might be a simple O2 sensor or MAP sensor failure. The gunk in the head sounds like it’s just a result of poor maintenance, and you seem to have replaced the appropriate parts to fix that. At least the diagnostic test will be able to eliminate a lot of potential things causing the excessive fuel usage, so you know where to focus your energy. If diagnostics come back clear, then clean the injectors etc

[NZWAKA]

Had a little bit of time yesterday, hooked up a smoke machine to the car and no leaks were found then using Dave's method I cleaned the injectors and checked the cold start injector which was 7.8 OHMS. I then ran a diagnostic test by bridging the two connections. Getting fault codes 24 and 31, as far as im aware 24 is the intake air temp sensor and 31 is the vaccum sensor to the ECU? What else can I check here?

[ollie83]

Ok, that’s good news for you mate. The MAP sensor is likely the cause of most of your issues. Replace both sensors and you’re car will run like a dream
Let us know how you get on


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[rebuilder86]

before u throe monry at thr sensor read this.

https://www.yotatech.com/forums/f116...4-31-a-212069/

little round relay. relays fail.

[NZWAKA]

Ok, that’s good news for you mate. The MAP sensor is likely the cause of most of your issues. Replace both sensors and you’re car will run like a dream
Let us know how you get on


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Replaced the MAP sensor from a bigport, no change. Also was going to replace the O2 sensor but the car doesn't have one...

ECU next?