Misfire after about 20 minutes

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

Strange goings on with my 90 at the moment. From cold it behaves normally however after about 20 minutes driving it starts to misfire and shudder intermittently. Seems to be when there is low load on the motor such as coasting on flat ground at 60 kph it is worst. Hold it back in 2nd gear (auto) at 60 with revs at about 3000 and all is well but if you put it back into drive , revs drop and misfire starts. Sometimes no problems, but others it's terrible. Have cleaned maf sensor, new air filter, going to do plugs tomorrow but any thoughts and similar experiences appreciated. Thought it may have been water in fuel so gave it a drink of metho into both tanks but that made no difference. Problem is there whether using main or sub tank.

[pradosteve97 Junior Member Find all posts View Profile Close pradosteve97]

Id look at the plug leads most Toyota's I ve worked on that are missing its leads.
I probably should add most of the Toyota's I've worked on would be Camry's so I maybe wrong.

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

So fitted new plugs today but the problem still remains. Don't have diagnostic tools but work with someone that may. Given the fact that it doesnt bring up the check engine light will it likely show anything in the diagnostics. All old plugs looked ok but gaps were a bit big on some which is understandable as they have done about 120 000 km.

[VKPrado Avid PP Poster! Find all posts View Profile Close VKPrado]

Have you tried replacing the plugs also? Might be a case of elimination but plugs and leads are always a good start and are on the cheap end of the scale when trying to find a problem.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

I would be looking at crank sensor, fuel injectors etc. The knock sensor start operating above 3000 rpm so when below 3000 rpm any misfire (creating detonation) from incorrect timing/fuel mix etc. will be felt, above 3000 rpm the system will compensate.

Lee

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

Have you tried replacing the plugs also? Might be a case of elimination but plugs and leads are always a good start and are on the cheap end of the scale when trying to find a problem.

Did the plugs today for no improvement. Probably go leads and coil packs next. eBay has 3 x coil packs for about $80.00. Much cheaper than genuine but not sure how good they are. Anyone here tried them?

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

I would be looking at crank sensor, fuel injectors etc. The knock sensor start operating above 3000 rpm so when below 3000 rpm any misfire (creating detonation) from incorrect timing/fuel mix etc. will be felt, above 3000 rpm the system will compensate.

Lee

Any way to check sensors and injectors without replacing. Would much prefer to prove the fault rather than just keep replacing parts till it goes away. Looks like removing injectors is a fairly major and time consuming task so would prefer to save that option till last!

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

Plugs or leads.
Sounds like leads.

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

Plugs or leads.
Sounds like leads.

Thanks ####, your knowledge and experience always appreciated
Leads are my next target.

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

These power loss, rough idle & misfiring issues are beginning to be raised one after the other for the higher kilometre 5VZ-FE engines lately. I hope you find out what it is without it costing you too much. I'm keen to find out myself what the cause is as this may be me one day. The 120 series petrol owners may begin to encounter this one day too as time goes on. I had a power loss and rough running engine a little while back when driving up steep hills above 60km/h, but that turned out to be my crank angle sensor. My ignition system was tip top. Be careful before replacing sensors as a part of elimination as they can be over $200 a pop. If it's not the spark plugs, leads or the coil packs, then maybe explore the valve timing with your car/cam shaft position sensor. It's located behind the timing cover under the driver's side cam shaft sprocket. But like I said, sensors are expensive so be sure first. I've read of a lot of people thinking it's the fuel pump with these sorts of issues but that rarely turns out to be the issue from my understanding. They're big bucks too and a pain in the arse to replace the in tank ones.

Can be difficult to find out the cause via the diagnostics plug with the 90 series. I've bridged ports before to find out what my issue was and counted the amount of times the check engine light flashed and it kept going for hundreds of times without stopping so came to the realisation it's not all that accurate at helping one with their problem diagnosis. That's where the automotive industry could be turned on its head with system error read outs in plain English that tell you exactly what the electrical or sensor problem is and how to fix it in modern cars. Even a constant looping read out on a little screen incorporated into the dash cluster would be a smart idea. With a long list of codes at present that can mean several things for the one error code isn't as sophisticated as it could be in this day and age. Maybe we'll have to wait another 20 or 30 years for that due to slow reaction from the automotive industry not wanting to get too advanced too early. Tiny little advancements at a time makes them a lot more money I suppose because it enables them to keep flogging off cars to the masses.

Good luck mate and I hope it turns out to be easier than Super Mario Brothers

[carco Advanced Member Find all posts View Profile Close carco]

Do these things have an igniter or is it built into the coil pack?
With Nissan stuff igniter problems only surfaced after about 20 minutes, temperature dependent.
They had poor/dry solder joints and could be fixed by dismantling and re-solding.
The Z cars were renowned for it until Nissan moved the igniter from the engine to the firewall, much cooler up there.
Nissan's later models had the igniters built into each individual coil pack.

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

Problem appears to be solved with a new set of leads. Fitted them and took it for a drive about 45 mins at various speeds and terrain and could not recreate the fault. Thanks all for your input.

[fishtank Junior Member Find all posts View Profile Close fishtank]

I've had the el cheapo power packs in for about 12 months now. No issues.