1999 Toyota Tacoma Low Compression?

Tiny
JEREMYCOERPER
  • MEMBER
  • 1999 TOYOTA TACOMA
  • 4 CYL
  • 4WD
  • MANUAL
  • 158,000 MILES
Hi. I live in the Bay Area, CA, and I think I’m having compression problems with my Tacoma. The mechanic I’ve been going to is not a Toyota-specialized mechanic – just a Mom and Pop place (all the work listed below was done by this guy except the idle air control valve). The check engine light has been on and his diagnosis is that cylinders 1 and 2 have low compression. His recommendation based on the age of the engine is that I get a new engine. So I would just like to have a second opinion before investing in that kind of expense. Here is a brief history which I hope will provide enough info for an informed opinion of the problem…

I bought the truck in 2004 from a contractor with about 90,000 miles on it. In hindsight, it probably wasn’t the best decision. The outside of the truck was pretty scratched up, so there’s probably a good chance he didn’t maintain it very well either.

I’ve taken decent care of it – usually changing the oil every 4K-5K miles, occasionally going to 6K if I forget.

The only major repair I had before was in March ’07 after it had sat unused for about 5 months (not sure if that was related). The idle air control valve had gone bad (causing high idling) and I had it replaced. A throttle body flush, air induction flush, and throttle body cleaning were also part of this repair.

The check engine light first went on about a year ago, but then it continued to cycle on and off – often staying off for days or weeks at a time – there were no other symptoms, so I didn’t worry too much about it. At some time after that, the idle started to stick a little high at times also (around 1,100 rpm).

In June ’09, after having an oil change, I noticed a very slow drip of oil for the first time. I took it back to the mechanic who said it looked to be coming from the oil pan. He said the new oil might be getting through a hole that could have developed a while ago which the older, thicker oil could not escape through. I believe the drip stopped after a week or two.

In August ’09, I had it emission-tested and it passed no problem.

In September ’09, I finally had the check engine light diagnosed which said that the throttle position sensor was bad. I had that replaced and the throttle body cleaned, and the check engine light stayed off after this. My mechanic recommended that after doing this work, I should have the sparkplugs and fuel filter replaced ASAP.

In October ’09, he replaced the AC/water pump belt, sparkplugs, wires, and fuel filter (immediately prior to this work, I put in a bottle of Lucas fuel injector cleaner, per his recommendation). It turned out the wires and fuel filter had never been replaced before! At this time he also did a compression check, I think because spark plugs 1 and 2 showed signs of mis-firing (slightly blackened). On the first check, the pressure was:
#1 – 70 PSI
#2 – 60 PSI
#3 – 180 PSI
#4 – 170 PSI

He sprayed some fluid in, and rechecked 1 and 2, which had then raised to:
#1 – 80 PSI
#2 – 100 PSI

At this time, the check engine light was still off, but about a week later, it came back on. He diagnosed it again. This time, the computer indicated a “random misfire" on cylinders 1 and 2. This brings us up the present and his final recommendation that the engine be replaced because either the piston rings are bad or something is possibly cracked.

I haven’t noticed any drop in power or any other symptoms, although I think my fuel economy is down. I switched from regular to premium gas for a few tanks to see if that would make a difference, but I haven’t noticed anything. On the last tank, I was averaging about 14 mpg, although it was mostly city driving, often with heavy loads – but that still seems low.

The only noises I’ve noticed are the same ones that have always been there since I bought the truck:
-knocking for the first 20 seconds or so after starting on very cold mornings
-occasional squeaking – maybe a belt?

The check engine light is still on, and a few times it has started flashing, seemingly related to high revving – either accelerating or engine braking.

So thank you if you’ve made it this far! Any insights to the problem and possible solutions would be greatly appreciated! If it seems likely to be a major expense (in the $1,000s), I’m considering selling the truck as is and upgrading. But it would be nice to keep it if a relatively inexpensive repair could remedy the problem.

Thanks,
Jeremy
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Sunday, December 13th, 2009 AT 2:09 AM

7 Replies

Tiny
RASMATAZ
  • MEMBER
You have 2 cylinders that are low and creating misfires due to rings/cylinder wear if its gonna be done other than you-get rid of it-its gonna cost over that amount-also you are in there there's other things that can be replace such as oil pump and engine bearings-you don't want to leave this things behind while in there. If you can get a short block for less than 1K go for it but remember you only did half of the engine, if you leave the upper end (the valve train) unconditioned it will not produce maximum full power/performance my opinion-Amen

NOTE: On the engine bearings might as well get a crank kit
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Sunday, December 13th, 2009 AT 3:09 AM
Tiny
MHPAUTOS
  • EXPERT
HI there,

We are basically looking at worn rings, with the comp test being done wet, he would have added some oil to temporally seal the ring lands, but as you can see the comps have not come up anywhere near the good two comps, so this will indicate a vale problem as well, saying that, I would like to see this done again and make sure that oil is added to each cylinder, as you said something was sprayed, I would like to know that oil was added for the test, With the valves being a possible issue as well, it is important to know that there are potential problems with just doing the head on older engines, as this can leads to excessive oil consumption problems, so what too do, if you want to keep the car in the short term, doing the head is an option if the rings are reasonably sound, the oil test will help with this, if you don't want to keep the car, just be rid of it and up date, at this stage I would like to see a new comp test doe wet with oil rather than something "sprayed" in,

Mark (mhpautos)
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Sunday, December 13th, 2009 AT 3:16 AM
Tiny
RASMATAZ
  • MEMBER
Hey Oz maybe he didn't do both tests and should follow it with a cylinder leakage tests too-about the spray maybe its WD-40 lol I've never triy it only 30 weight oil
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Sunday, December 13th, 2009 AT 3:29 AM
Tiny
MHPAUTOS
  • EXPERT
Yes, spray lube is not thick enough, you need engine oil 30 weight would be good, just as long as you can seal up the ring lands for the test.

Mark.
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Sunday, December 13th, 2009 AT 6:30 AM
Tiny
JEREMYCOERPER
  • MEMBER
Thanks for the info. Regarding the compression test, I'm not sure what fluid he used. After checking my notes again, what he said was that he "added a fluid, " so I don't think it was sprayed actually.

I wouldn't do any of the work myself, so I'm really just trying to find out if my mechanic's diagnosis sounds accurate and if his recommendation to replace the engine sounds like the best solution, or if there is a cheaper option. It sounds like probably not?
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Sunday, December 13th, 2009 AT 12:43 PM
Tiny
RASMATAZ
  • MEMBER
You got 2-bad cylinders -either you replace it with a reman or get one from the junkyard dogs-Good LUCK
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Sunday, December 13th, 2009 AT 12:52 PM
Tiny
JEREMYCOERPER
  • MEMBER
Thanks for your response on Dec. 13 regarding my Tacoma with poor compression. I had a follow-up question. Is it possible some grit or something got into one of the valves which is causing the poor compression? I'm asking b/c as I mentioned, the fuel filter had never been changed before, and this all happened right after the throttle body was cleaned. If this is the problem, could running premium gas for a while and/or using fuel injector-cleaner clean it out? Would it hurt to try? Or is there some other product I could try that wouldn't hurt anything? Alternatively, if the valves need to be adjusted, could this cause poor compression? And how much would it cost to have the valves adjusted? Thanks again.
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Monday, January 4th, 2010 AT 2:39 PM

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