Hesitation before boost

Post by **Alspos** » Fri Jun 21, 2013 5:09 pm

All has been ok, yesterday drove the car, after it was half warm it would misfire once I started to get into positive boost. Seemed to get worse when the car got warmer. Didn't matter what gear, as soon as it saw the orange the car backfires a bit, misfires and all power goes (like when a car runs out of fuel) Back off and it runs fine. Car does rev up to 5k rpm without getting into boost (in second gear)

Car is half full of fuel (98), new plug leads installed yesterday. I've checked all inlet hoses for tight clamps, split hoses, all appears ok. All vacuum lines, pollution lines appear to be in place.

Where do I check next?
TPS?
Fuel pressure reg?
Fuel pump?

POS car..... :x

Schultz · Post by **Schultz** » Fri Jun 21, 2013 7:15 pm

I had the same problem with my MPI system a while ago. I had a broken wire going to the injectors. Found it after I pulled on the wires a bit, I was moving them out of the way to see if I had a vac hose off somewhere.

JDSTAZ45 · Post by **JDSTAZ45** » Fri Jun 21, 2013 8:16 pm

I'm not sure what precautions you did while your car was a garden ornament, but my guess it's the fuel tank combined with a on-the-way-out fuel pump.
When you add the 98 octane fuel, it usually tends to release the crap in the fuel tank (if on the verge on decaying) with the additives in with the fuel.
Some of the cars I've brought in from Japan have been sitting around for a while and have had the same symptoms.
Consequently, I've had to flush tanks out or even replace them and have new fuel pumps installed.

The fpr should be checked under load to see there is drop in pressure.
So in all, I think your fuel delivery is causing the hesitation and will get worse the longer you leave it.
I can see another brilliant 'how to fix' from Al.

:beer Mal

Post by **Alspos** » Fri Jun 21, 2013 8:25 pm

I have had the fuel tank out and it was cleaned along with the fuel pick up and filter (about a year or so ago when I decided to get into getting it going properly) I also added a big ass fuel filter before the fuel pump (after I flucked one from probably sucking up crap)

How does one check fuel pressure under load...I assume it's a dyno type trick or any number of weird ass fittings and adaptors.

I hope I have a spare FPR....see what I can dig out. The pump is a stockie from memory. Maybe a newie is on the cards just from a piece of mind point of view. Hmmm....

JDSTAZ45 · Post by **JDSTAZ45** » Fri Jun 21, 2013 9:52 pm

Yeah I mean to have the fuel pressure checked with some meter thingy that mechanics tend to have. Usually checking it with the revs up. The fpr should be fine.
I had my tank cleaned out but not everything was completely removed. And with additives in today's fuels it tends to release more crap.

If a new fuel pump is put in, give it another check if not another flush!
Is the pump getting noisy or beginning to struggle with a noticeable drone?

However, we are dealing with a JA here and it could be a number of things...

kailo · Post by **kailo** » Fri Jun 21, 2013 10:42 pm

thought of looking into the common map sensor issue.. sound odd from description no boost at 5k.. unless i misinterpreted what you meant

Post by **Alspos** » Fri Jun 21, 2013 11:11 pm

kailo wrote:thought of looking into the common map sensor issue.. sound odd from description no boost at 5k.. unless i misinterpreted what you meant

yeah, I think you misunderstood... I can run the engine to 5k as long as I don't go into positive boost (so, second gear on a flat bit of road)

Komeuppance · Post by **Komeuppance** » Sat Jun 22, 2013 8:42 am

I looked at your engine bay pics and didn't see that your wastegate had a vac line, though it might be hard to see. You might be hitting fuel cut if your wastegate isn't working properly.

If that checks out, a boost leak test would be the next step, pressurizing your piping system with an air compressor and adapter.

After that, a fuel pressure test while driving. You'll need to tap into the fuel line before the FPR and watch the gauge as you get into boost. A temporary setup taped to the windshield will not cost very much ($10-15 over here). Pretty sure the ECU does fuel cut by shutting off the pump, so make sure your wastegate is working properly.

The following wont prevent boost entirely, but will cause a hesitation before getting into boost. Make sure your FPR vac line has the correct source, a port before the throttle plate. And your dizzy's vac line is connected to the correct source, on 2.6's its a restricted port.

-Robert

thrash · Post by **thrash** » Sat Jun 22, 2013 4:17 pm

I forget, doesn't the system switch from maf to map (or start using one of them to fine tune) when coming on boost?

If so, this may have something to do with it?

popup · Post by **popup** » Sat Jun 22, 2013 10:56 pm

thrash wrote:I forget, doesn't the system switch from maf to map (or start using one of them to fine tune) when coming on boost?

If so, this may have something to do with it?

I was thinking the same thing, I read that somewhere recently. However, I think there is a lot unknown about how these ECUs work and the changes through the years,so I take it all with a pinch of salt. There must be something in FSM or supplement on checking all the sensors? I think thats the only way to diagnose, go through each component one by one.

enthuzed · Post by **enthuzed** » Tue Jun 25, 2013 9:29 pm

Sounds like a dodgy secondary injector Al. Flow moreso than wiring. A bitch on a JA...

mizuno man · Post by **mizuno man** » Wed Jun 26, 2013 5:20 pm

Could be your coil as well.

Post by **Alspos** » Wed Jun 26, 2013 6:33 pm

Played with the pos today....

Checked TPS...reads 1K to 4K ohms...good
Checked injector connector...cleaned things...good
Checked dizzy, vac advance module (with bike pump)....good
Pulled a few other connectors...cleaned...good
Checked BOV line for leaks...good

Went for a drive.....pos carried on a bit like before but I managed to make it happen more consistantly. 3/4 throttle with boost in 1st and 2nd gear, would stumble consistently at 2.5k. Less throttle and it would complain a little later in the rev range (3-3.5k)

Then, I was idling waiting for a gap in the traffic before launching the flucker into the neighbours house I noticed a weird sound....the fuel pump was buzzing...then would stop for half a sec....buzz for about a second...bzzt...bzzt... I haven't noticed the noise for a while, it's normally fairly quiet but obviously this is my issue, s'pose it's about the only bit I haven't replaced with new or rebuilt bits so it's bound to fail!

So I guess my next step is replace both fuel filters and find a fuel pump. Oh well, it's only money...

Thank you all for the input...made me think and check off a fair amount of things to ensure that everything is ok.

JDSTAZ45 · Post by **JDSTAZ45** » Wed Jun 26, 2013 7:10 pm

A range of fuel pumps have just come on Aust ebay recently for around a $100 bucks.
http://www.ebay.com.au/itm/Mitsubishi-S ... 53fa4b9df0
Rubber sleeve missing in pic??

Drop the tank while replacing the fuel pump. Check filters and flush/replace fuel. I suggest in not using Shell as it tends to have the most additives.

I hope this fixes the problem over being something else such as a leaking injector etc.

:beer

Post by **Alspos** » Wed Jun 26, 2013 9:16 pm

Has anyone installed one of these? There's no data about fuel flow rates or anything...just a tad worried if I decide to change to MPI in future whether it will cope with the extra fuel requirements.

Also.....they're here .... http://www.mdsperformance.com.au/produc ... it-PIP-321

Austarion

Hesitation before boost

Hesitation before boost

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