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mk1b no acceleration past 3k RPM

 
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chrismit




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PostPosted: Sun Feb 19, 2017 4:43 pm    Post subject: mk1b no acceleration past 3k RPM Reply with quote Reply with quote including images

Hello

Been working at getting my mk1 back on the road after not being mot'd and sat for 8 years before i bought it.

Im having an issue at the moment with the car bogging down after 3k RPM in any gear except first which will allow you to accelerate to about 5k then it will also have the same problem.

Symptoms are car is accelerating as you would expect then just starts bogging down and popping can be heard from the exhaust and there is no further increase in speed in that gear. Until you upshift and can accelerate again below the 3k.

The car will drive around part throttle fine with no issues below the 3k mark. Its just WOT under load i am guessing the issue occurs.

So far i have changed the spark plugs, the leads, the rotor cap and arm.

I have re done the grounds on the vehicle and alternator to positive terminal.

I have cleaned the contacts on the ignitier.

I have also suspected timing but i dont seem to be able to see the timing marks from above as the engine mount seems to be blocking my view. I would like to check this anyway so if someone has a guide they could link id appreciate it as i seem to be able to find alot of videos relating to the same engine in the corolla but not for the MR2.

Due to the fact the exhaust is popping i am ruling out a fueling problem as it will be running rich to cause that condition rather than lean i imagine. I have replaced the fuel pump which was what initially was stopping the car from starting.

Any suggestions would be appreciated before i go buying more bits to try.

Thanks

Chris
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PW@Woodsport
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PostPosted: Mon Feb 20, 2017 7:07 am    Post subject: Reply with quote Reply with quote including images

Very first port of call is pulling the fault codes, bridge T and E1 in the diagnostic connector, switch ignition on, count check engine light flashes, fault code 4 will be 4 flashes etc, no codes stored will be constant single flash.

Presumably the car was running perfectly 8 years before when it was parked up? Or has at one point been running perfectly during your ownership?
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chrismit




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PostPosted: Mon Feb 20, 2017 10:01 am    Post subject: Reply with quote Reply with quote including images

Don't know why I didn't think to do that in the first place, i'll have a go when I get back from work and post the results.

Yes the previous owner had it driving around fine and then just parked it up, this is the first time I have had it on the road, I noticed this on the way to the MOT station.
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chrismit




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PostPosted: Mon Feb 20, 2017 3:58 pm    Post subject: Reply with quote Reply with quote including images

[quote="PW@Woodsport"]Very first port of call is pulling the fault codes, bridge T and E1 in the diagnostic connector, switch ignition on, count check engine light flashes, fault code 4 will be 4 flashes etc, no codes stored will be constant single flash.

So just done this and i am getting a single flash, every 3 seconds or so, i havent pulled any fuses or disconnected the battery since it happened.

So looks like no fault codes stored
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PW@Woodsport
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PostPosted: Mon Feb 20, 2017 5:13 pm    Post subject: Reply with quote Reply with quote including images

Ok, next thing I would do in my workshop is check the fuel pressure with a proper gauge inline after the filter.... but presuming the fuel pressure is good (it would cause your symptoms by the way) , as a quick check, look at the vacuum feed line to your MAP sensor mounted on the boot wall just on the right, the rubber line going to it attaches to a metal tube bolted to the side of the inlet manifold, this tube often cracks, which throws your fuelling way out.

I'm not saying that is it, but a quick and easy thing to check.
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chrismit




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PostPosted: Mon Feb 20, 2017 7:14 pm    Post subject: Reply with quote Reply with quote including images

Thanks for the reply

Funny you should mention fueling i was thinking that,

The fuel pump unit i used to replace was a walbro 255 unit i had laying around for my turbo mk2.

But my thoughts are that the FPR would return any excessive fuel to the tank via the return pipe and the pressure would be the same in the rail. Unless the FPR is not working as intended?
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PW@Woodsport
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PostPosted: Tue Feb 21, 2017 7:23 am    Post subject: Reply with quote Reply with quote including images

Ohh... a 255, that's massive overkill, your stock Mk1 pump delivers around 80lph, so the walbro is delivering over 3 times the fuel you need!

Now in theory the regulator should be keeping the pressure constant, but you are moving so much fuel to the rail it could be overcoming the regulator..... ie it cannot reduce the pressure sufficiently. The problem is made worse by the fact a 4a-ge has no closed loop fuel control, in other words no lambda sensor to tell the ECU how the last cycle of fuel was burnt so that it can throttle up or down the injector duty to adjust (short and long term fuel trim values on more advanced engines). It simply calculates the amount of fuel needed for a given pressure v TPS position and MAP sensor reading...... it's a very basic system and actually only one step up from having a carb on there.

It could be your regulator is faulty, but I have never seen this, but I 100% would advise fitting a stock fuel pump, even if it isn't the issue you will be circulating unused fuel back to the tank like crazy! Your engine acts like a boiler and running fuel through it back to the tank will slowly heat it up, creating lots of vapour, it all isn't good really.

Your issue could be something else, just giving this my best shot via the internet, but I personally would be changing that fuel pump to stock.
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chrismit




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PostPosted: Wed Feb 22, 2017 9:46 am    Post subject: Reply with quote Reply with quote including images

In regards to all the vac lines I have changed those.

Does make sense what you've said its a lot of fuel to just be recirculating, I think I will probably end up changing the fuel pump back, although not a real fun process dropping that tank out on my garage floor just on axle stands.

I do have a variable FPR in the garage, I might try hooking that up and see if maybe the regulator has gone faulty before I do drop the tank again. From reading the stock pressure should be around 35-38 psi?

Thanks again
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PW@Woodsport
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PostPosted: Thu Feb 23, 2017 7:49 am    Post subject: Reply with quote Reply with quote including images

Yes that pressure is correct, trying a FPR is probably a good idea, but you will need to remove the old regulator from the rail too.
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chrismit




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PostPosted: Fri Feb 24, 2017 11:28 am    Post subject: Reply with quote Reply with quote including images

Will be fitting it tonight, got a fuel rail adapter with it for the rail. So will see how I get on.
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chrismit




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PostPosted: Sat Feb 25, 2017 1:52 pm    Post subject: Reply with quote Reply with quote including images

Okay so tried another FPR and still the same thing is occuring, it is a known working regulator but i guess i do need to still try and read the fuel pressure properly

Seen as this is the tvis model could it have anything to do with that maybe being stuck and not opening to allow more air flow? even if that didnt open though i imagine it would still slowly increase in speed and rpm and not just hit a wall?
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PW@Woodsport
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PostPosted: Sun Feb 26, 2017 9:52 am    Post subject: Reply with quote Reply with quote including images

No it's not Tvis related at all, you can rule that out.

This type of problem is extremely hard to fix via the internet, I would need to spend time on it in person I think.
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aw11rally




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1984 Toyota MR2 Mk1a

PostPosted: Sun Feb 26, 2017 8:07 pm    Post subject: Reply with quote Reply with quote including images

Are you sure the pump that you fitted is good?

This sounds like similar symptoms I've had with a failing standard pump.

I've also had similar problems with a dodgy MAP sensor, although not on an mr2.
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chrismit




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PostPosted: Tue Feb 28, 2017 9:22 am    Post subject: Reply with quote Reply with quote including images

I cant be sure. I mean it was new out of the packet and into the car but it could potentially be bad I suppose.

I know it is supplying fuel as the car is running and I can empty my tank by removing the return line but maybe its just bad and not able to keep up with the fueling.

Cant seem to get a replacement oe pump through my local parts place though.

Id probably consider bringing it to you Paul but without an mot, getting it towed would be quite expensive, i'll probably just continue on. Going to try unplug the TPS later see if that makes any difference.
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