'91 Tracker misfires & hard to start...

[macbd1]

A long post but how else to fully describe the situation, and maybe a learning experience?

Have a '91 Tracker (120k miles, non-CA, non-emission test state) 4WD manual 5 speed w/ 1.6L SB FI engine, a great little vehicle that we have enjoyed on and off-road for 16 years, have taken many trips + pulled behind motor home, can't say enough good things, it's a fun vehicle that will go anywhere in 4WD low.

Have been lazy with maintenance (except for oil changes) for 4 yrs or so, it just kept running great so I let it. But recently when backing out of a parking space the engine seemed to suddenly 'let go' slightly (as if a component broke, choked up or quit) accompanied by a slight but noticable power drop, and a random engine misfire has since occurred.

The 2-yr old muffler had just become a little noisy that week and I recall a similar immediate loss of power (but no misfires) when a muffler 'blew a hole' on the highway in recent years (the engine returned to normal with a new muffler & tail pipe), so I had the muffler replaced – the dealer said there was no warranty but that he would only charge his cost of $30 - but this did not ‘fix’ the misfires. (The technician said the muffler innards were apparently ‘shot,’ by shaking the muffler, but the exterior appearance was still like new, the slight exhaust noise was apparently from the weep hole or possibly even from the flange ahead of the muffler, or so it seemed to me while Tracker was on the ground – he slightly tack-welded this slipping flange-joint.)

Another symptom after the ‘let go’ power drop (also after new muffler) was that the idle speed had also dropped to about 300-400 rpm after warming up – barely running. The cold-engine rpm was also lower than usual (although it never was very high, maybe 1200-1400 rpm before the problem, 900-1100 rpm after.) The engine would almost stall if I didn’t ‘feather it’ (slightly accelerate carefully) during warmup from cold start.

I then provided TLC with new plugs & wires, dist. cap & rotor, air filter, PCV, valve adj (surprisingly not far from spec. & no clattering), timing adj and troubleshooting for vac leaks and fuel/emission component tests -- but the 'random' misfires remain at all speeds. It runs great after warming up and responds with ‘no’ hesitation to quick full throttle - the misfires are not very noticeable at driving speeds but slight ‘bucking’ exists when down-shifting at very slow speeds.

I adjusted the throttle-opener to about 1800 rpm (for hopefully better starting) and the curb-idle to about 1000 rpm (to cover for misfires at idle, it should be 800) – but cold-starts are still difficult although the engine ‘always’ starts when I ‘feather’ the engine for 20-30 seconds during warmup. It starts immediately when engine is hot, but stumbles a little due to misfiring.

When removing sparkplugs while idling, each cylinder drops rpm slightly by the same amount, and the spark at each plug (to ground) seems equally steady and strong. So, I suspect neither problem is of electrical/ignition nature.

I cleaned the EGR and Vacuum Modulating valves of soot (including ports, one was blocked, plus interior of the intake manifold as far as I could reach) and they now seem to work ok, from pressure and vacuum-gun tests per the Haines manual.

With full manifold vacuum or vac-gun directly connected to the EGR, the diaphram responds smoothly as it should. I do wonder about the EGR-vsv for the hose running to the Modulator Valve ahead of the EGR as the vacuum gauge reads only 5-10” Hg when the hot engine is revved and the EGR should be opening -- although I can’t see or feel the diaphram moving, it appears the EGR may remain closed all the time. (All vac hoses are clear and tight although I did have to blow a slight soot blockage out of the larger exhaust gas hose from the EGR to Vac. Modulator Valve.)

Intake manifold vacuum runs ‘rock-steady’ at 19” Hg at idle. It increases to about 23” Hg when increasing idle slowly to about 2000 rpm but vacuum doesn’t increase further at higher rpm. However, ‘quickly’ increasing rpm from idle causes a quick dip or decrease toward zero in vacuum gauge needle which then steadily recovers to about 22-23” Hg over 3-4 seconds. Am I correct that this ‘drop’ may indicate a possible EGR problem or exhaust blockage, I’m unsure though what the ‘recovery’ indicates?

The misfires are fast-paced and constant at any rpm but with no apparent pattern. The tach will quickly jump ‘upward’ by about 500rpm (at idle) consistently, but infrequently, while a series of upward 100-200 rpm ‘blips’ occur more frequently – intermixed with occasional upward blips of 350 rpm or so, again these are fast-paced. The blips are always present but become progressively less noticeable (maybe 30-50 rpm on the tach) as rpm is increased.

A complicating factor here is that the Check Engine light came on steady a few years ago. However, after cleaning contacts of the test-connector to bright metal and jumpering the #2 to #3 terminals per the manual, the light does not flicker to indicate any codes, not even the ‘engine-ok’ code. When this first happened at about 80k miles I assumed it was a maintenance-needed warning as the engine continued to run great along with no drop in gas mileage or other indications of engine problems. This status has not changed so I do not know what codes the ECM may or may not be trying to generate. Removing the negative battery terminal for several minutes has no effect, the Check Engine light is steadily present when first turning the key to ‘on,’ or starting.

So…I’m now stuck with a hard-starting engine with winter temp’s coming soon, plus the misfire problem. I maybe will have to live with this as I don’t intend to spend several hundred dollars on this old vehicle, and maybe I will even give up this old friend. For example, a new EGR & Vac. Mod. Valve totals about $350 alone around my area. The O2 sensor should have already been changed twice at 60k miles per the manual - $100 OE + $12 for a deep socket removal tool.

I’m presently running with fuel injector cleaner in the tank. I’ll try fine-tuning the throttle-opener and idle-speed again although I know several things or components can cause the air-fuel mix to go lean at starting. Components I will try to test further:

O2 sensor, EGR & Mod + vsv, coolant temp sensor, fuel injector, fuel pressure regulator, also fuel pump pressure and filter – also catalytic converter. However, the strong operation of the engine after tuneup, its responsive acceleration and nice operation at high rpm indicates to me that fuel pressure is not a contributer to either problem.

Oh, the single fuel injector provides a large cone-shaped fuel-spray, or at least the tiny droplet ‘splashes’ onto the entire area of the throttle plate makes it appear so, my eyesight is not like it used to be.

Does anyone have knowledge of what else might be causing the sudden misfiring and hard start problems – both seem to be factors of air-fuel mix to me…??

Thanks for taking time to read this, and of course any help,
Have a good one,

Mac
PS – Maybe I can get AutoZone to scan the codes, if any are present? It’s been so long since I’ve had engine problems with any vehicle that I’m kinda lost.

[macbd1]

View the following link (where I posted the same intro-description as here) for lots of info on older Trackers and how my problems were resolved:

http://www.suzuki-forums.com/suzuki-...ard-start.html

Mac

[captabad1]

My jgc laredo 4.0 L 1998 went on to start the check engine ligth no lit